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	$248.91	9.141%	$271.6629	$271.66	$271.65	$271.70
Purchase #2	$33.97	10.349%	$37.4856	$37.49	$37.50	$37.50
Purchase #3	$162.71	6.819%	$173.8052	$173.81	$173.80	$173.80
Purchase #4	$45.59	3.538%	$47.203	$47.20	$47.20	$47.20
Purchase #5	$153.96	10.383%	$169.9457	$169.95	$169.95	$169.90
Purchase #6	$165.37	12.365%	$185.818	$185.82	$185.80	$185.80
Purchase #7	$138.44	9.318%	$151.3398	$151.34	$151.35	$151.30
7 purchase totals =	$948.95		$1,037.2602	$1,037.27	$1,037.25	$1,037.20