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	$206.41	10.531%	$228.147	$228.15	$228.15	$228.10
Purchase #2	$112.98	4.241%	$117.7715	$117.77	$117.75	$117.80
Purchase #3	$45.47	3.121%	$46.8891	$46.89	$46.90	$46.90
Purchase #4	$199.70	5.715%	$211.1129	$211.11	$211.10	$211.10
Purchase #5	$214.65	4.128%	$223.5108	$223.51	$223.50	$223.50
Purchase #6	$95.99	3.570%	$99.4168	$99.42	$99.40	$99.40
Purchase #7	$42.47	8.127%	$45.9215	$45.92	$45.90	$45.90
7 purchase totals =	$917.67		$972.7696	$972.77	$972.70	$972.70