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	$238.51	7.663%	$256.787	$256.79	$256.80	$256.80
Purchase #2	$108.96	3.399%	$112.6636	$112.66	$112.65	$112.70
Purchase #3	$234.76	11.735%	$262.3091	$262.31	$262.30	$262.30
Purchase #4	$96.49	5.788%	$102.0748	$102.07	$102.05	$102.10
Purchase #5	$126.77	4.388%	$132.3327	$132.33	$132.35	$132.30
Purchase #6	$98.48	13.492%	$111.7669	$111.77	$111.75	$111.80
Purchase #7	$184.76	12.316%	$207.515	$207.52	$207.50	$207.50
7 purchase totals =	$1,088.73		$1,185.4491	$1,185.45	$1,185.40	$1,185.50