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	$121.60	7.818%	$131.1067	$131.11	$131.10	$131.10
Purchase #2	$24.80	8.425%	$26.8894	$26.89	$26.90	$26.90
Purchase #3	$32.28	10.343%	$35.6187	$35.62	$35.60	$35.60
Purchase #4	$112.89	12.795%	$127.3343	$127.33	$127.35	$127.30
Purchase #5	$248.56	6.534%	$264.8009	$264.80	$264.80	$264.80
Purchase #6	$108.75	4.428%	$113.5655	$113.57	$113.55	$113.60
Purchase #7	$37.40	12.159%	$41.9475	$41.95	$41.95	$41.90
7 purchase totals =	$686.28		$741.2630	$741.27	$741.25	$741.20