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	$39.46	4.694%	$41.3123	$41.31	$41.30	$41.30
Purchase #2	$133.54	6.106%	$141.694	$141.69	$141.70	$141.70
Purchase #3	$182.69	9.508%	$200.0602	$200.06	$200.05	$200.10
Purchase #4	$47.65	11.670%	$53.2108	$53.21	$53.20	$53.20
Purchase #5	$61.84	10.322%	$68.2231	$68.22	$68.20	$68.20
Purchase #6	$249.47	11.633%	$278.4908	$278.49	$278.50	$278.50
Purchase #7	$250.30	11.113%	$278.1158	$278.12	$278.10	$278.10
7 purchase totals =	$964.95		$1,061.1070	$1,061.10	$1,061.05	$1,061.10