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	$179.39	9.610%	$196.6294	$196.63	$196.65	$196.60
Purchase #2	$201.30	10.615%	$222.668	$222.67	$222.65	$222.70
Purchase #3	$129.88	13.409%	$147.2956	$147.30	$147.30	$147.30
Purchase #4	$81.83	9.129%	$89.3003	$89.30	$89.30	$89.30
Purchase #5	$219.77	4.547%	$229.7629	$229.76	$229.75	$229.80
Purchase #6	$127.54	6.161%	$135.3977	$135.40	$135.40	$135.40
Purchase #7	$221.43	10.368%	$244.3879	$244.39	$244.40	$244.40
7 purchase totals =	$1,161.14		$1,265.4418	$1,265.45	$1,265.45	$1,265.50