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	$35.30	5.293%	$37.1684	$37.17	$37.15	$37.20
Purchase #2	$64.94	10.389%	$71.6866	$71.69	$71.70	$71.70
Purchase #3	$44.96	3.248%	$46.4203	$46.42	$46.40	$46.40
Purchase #4	$140.64	11.289%	$156.5168	$156.52	$156.50	$156.50
Purchase #5	$248.88	9.242%	$271.8815	$271.88	$271.90	$271.90
Purchase #6	$222.87	11.221%	$247.8782	$247.88	$247.90	$247.90
Purchase #7	$46.88	10.295%	$51.7063	$51.71	$51.70	$51.70
7 purchase totals =	$804.47		$883.2581	$883.27	$883.25	$883.30