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	$122.86	6.529%	$130.8815	$130.88	$130.90	$130.90
Purchase #2	$72.70	7.386%	$78.0696	$78.07	$78.05	$78.10
Purchase #3	$85.95	6.356%	$91.413	$91.41	$91.40	$91.40
Purchase #4	$119.35	7.153%	$127.8871	$127.89	$127.90	$127.90
Purchase #5	$132.59	3.704%	$137.5011	$137.50	$137.50	$137.50
Purchase #6	$221.96	3.655%	$230.0726	$230.07	$230.05	$230.10
Purchase #7	$176.75	8.152%	$191.1587	$191.16	$191.15	$191.20
7 purchase totals =	$932.16		$986.9836	$986.98	$986.95	$987.10