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	$67.70	6.158%	$71.869	$71.87	$71.85	$71.90
Purchase #2	$122.49	4.166%	$127.5929	$127.59	$127.60	$127.60
Purchase #3	$49.92	9.487%	$54.6559	$54.66	$54.65	$54.70
Purchase #4	$165.32	9.219%	$180.5609	$180.56	$180.55	$180.60
Purchase #5	$95.57	12.775%	$107.7791	$107.78	$107.80	$107.80
Purchase #6	$71.73	13.813%	$81.6381	$81.64	$81.65	$81.60
Purchase #7	$132.65	5.140%	$139.4682	$139.47	$139.45	$139.50
7 purchase totals =	$705.38		$763.5641	$763.57	$763.55	$763.70