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	$164.58	11.365%	$183.2845	$183.28	$183.30	$183.30
Purchase #2	$51.37	13.439%	$58.2736	$58.27	$58.25	$58.30
Purchase #3	$243.87	11.484%	$271.876	$271.88	$271.90	$271.90
Purchase #4	$93.46	6.663%	$99.6872	$99.69	$99.70	$99.70
Purchase #5	$130.30	6.812%	$139.176	$139.18	$139.20	$139.20
Purchase #6	$59.65	8.490%	$64.7143	$64.71	$64.70	$64.70
Purchase #7	$247.92	10.740%	$274.5466	$274.55	$274.55	$274.50
7 purchase totals =	$991.15		$1,091.5582	$1,091.56	$1,091.60	$1,091.60