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	$70.53	3.264%	$72.8321	$72.83	$72.85	$72.80
Purchase #2	$42.84	10.300%	$47.2525	$47.25	$47.25	$47.30
Purchase #3	$166.31	3.837%	$172.6913	$172.69	$172.70	$172.70
Purchase #4	$184.91	5.656%	$195.3685	$195.37	$195.35	$195.40
Purchase #5	$250.32	3.756%	$259.722	$259.72	$259.70	$259.70
Purchase #6	$222.46	11.155%	$247.2754	$247.28	$247.30	$247.30
Purchase #7	$86.26	12.583%	$97.1141	$97.11	$97.10	$97.10
7 purchase totals =	$1,023.63		$1,092.2559	$1,092.25	$1,092.25	$1,092.30