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	$157.61	8.231%	$170.5829	$170.58	$170.60	$170.60
Purchase #2	$180.63	5.178%	$189.983	$189.98	$190.00	$190.00
Purchase #3	$131.37	7.635%	$141.4001	$141.40	$141.40	$141.40
Purchase #4	$229.96	5.620%	$242.8838	$242.88	$242.90	$242.90
Purchase #5	$128.60	3.654%	$133.299	$133.30	$133.30	$133.30
Purchase #6	$151.50	7.242%	$162.4716	$162.47	$162.45	$162.50
Purchase #7	$134.41	12.238%	$150.8591	$150.86	$150.85	$150.90
7 purchase totals =	$1,114.08		$1,191.4795	$1,191.47	$1,191.50	$1,191.60