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	$77.48	10.199%	$85.3822	$85.38	$85.40	$85.40
Purchase #2	$157.39	11.281%	$175.1452	$175.15	$175.15	$175.10
Purchase #3	$97.74	8.417%	$105.9668	$105.97	$105.95	$106.00
Purchase #4	$156.33	9.636%	$171.394	$171.39	$171.40	$171.40
Purchase #5	$247.90	3.788%	$257.2905	$257.29	$257.30	$257.30
Purchase #6	$37.65	9.299%	$41.1511	$41.15	$41.15	$41.20
Purchase #7	$153.80	7.789%	$165.7795	$165.78	$165.80	$165.80
7 purchase totals =	$928.29		$1,002.1093	$1,002.11	$1,002.15	$1,002.20