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	$249.37	5.286%	$262.5517	$262.55	$262.55	$262.60
Purchase #2	$169.50	3.418%	$175.2935	$175.29	$175.30	$175.30
Purchase #3	$33.95	11.188%	$37.7483	$37.75	$37.75	$37.70
Purchase #4	$165.26	5.728%	$174.7261	$174.73	$174.75	$174.70
Purchase #5	$65.47	11.222%	$72.817	$72.82	$72.80	$72.80
Purchase #6	$183.45	7.173%	$196.6089	$196.61	$196.60	$196.60
Purchase #7	$71.30	7.221%	$76.4486	$76.45	$76.45	$76.40
7 purchase totals =	$938.30		$996.1941	$996.20	$996.20	$996.10