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	$86.40	13.569%	$98.1236	$98.12	$98.10	$98.10
Purchase #2	$150.61	5.579%	$159.0125	$159.01	$159.00	$159.00
Purchase #3	$31.89	5.170%	$33.5387	$33.54	$33.55	$33.50
Purchase #4	$75.35	6.373%	$80.1521	$80.15	$80.15	$80.20
Purchase #5	$221.30	7.742%	$238.433	$238.43	$238.45	$238.40
Purchase #6	$137.81	12.786%	$155.4304	$155.43	$155.45	$155.40
Purchase #7	$232.75	3.348%	$240.5425	$240.54	$240.55	$240.50
7 purchase totals =	$936.11		$1,005.2328	$1,005.22	$1,005.25	$1,005.10