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	$223.83	8.754%	$243.4241	$243.42	$243.40	$243.40
Purchase #2	$72.98	5.452%	$76.9589	$76.96	$76.95	$77.00
Purchase #3	$35.85	5.786%	$37.9243	$37.92	$37.90	$37.90
Purchase #4	$45.73	3.507%	$47.3338	$47.33	$47.35	$47.30
Purchase #5	$126.58	4.820%	$132.6812	$132.68	$132.70	$132.70
Purchase #6	$44.27	3.620%	$45.8726	$45.87	$45.85	$45.90
Purchase #7	$112.30	12.298%	$126.1107	$126.11	$126.10	$126.10
7 purchase totals =	$661.54		$710.3056	$710.29	$710.25	$710.30