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	$236.84	5.494%	$249.852	$249.85	$249.85	$249.90
Purchase #2	$153.79	3.670%	$159.4341	$159.43	$159.45	$159.40
Purchase #3	$85.73	6.563%	$91.3565	$91.36	$91.35	$91.40
Purchase #4	$184.66	3.609%	$191.3244	$191.32	$191.30	$191.30
Purchase #5	$156.82	5.504%	$165.4514	$165.45	$165.45	$165.50
Purchase #6	$92.80	7.290%	$99.5651	$99.57	$99.55	$99.60
Purchase #7	$181.50	4.429%	$189.5386	$189.54	$189.55	$189.50
7 purchase totals =	$1,092.14		$1,146.5221	$1,146.52	$1,146.50	$1,146.60