Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$91.59	11.478%	$102.1027	$102.10	$102.10	$102.10
Purchase #2	$179.86	11.377%	$200.3227	$200.32	$200.30	$200.30
Purchase #3	$108.54	10.278%	$119.6957	$119.70	$119.70	$119.70
Purchase #4	$115.70	11.108%	$128.552	$128.55	$128.55	$128.60
Purchase #5	$135.52	3.523%	$140.2944	$140.29	$140.30	$140.30
Purchase #6	$181.41	10.201%	$199.9156	$199.92	$199.90	$199.90
Purchase #7	$205.90	11.427%	$229.4282	$229.43	$229.45	$229.40
7 purchase totals =	$1,018.52		$1,120.3113	$1,120.31	$1,120.30	$1,120.30