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	$239.92	6.216%	$254.8334	$254.83	$254.85	$254.80
Purchase #2	$250.33	11.275%	$278.5547	$278.55	$278.55	$278.60
Purchase #3	$21.85	5.131%	$22.9711	$22.97	$22.95	$23.00
Purchase #4	$56.94	4.797%	$59.6714	$59.67	$59.65	$59.70
Purchase #5	$111.65	7.861%	$120.4268	$120.43	$120.45	$120.40
Purchase #6	$22.55	5.632%	$23.82	$23.82	$23.80	$23.80
Purchase #7	$238.27	5.211%	$250.6862	$250.69	$250.70	$250.70
7 purchase totals =	$941.51		$1,010.9636	$1,010.96	$1,010.95	$1,011.00