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	$211.33	5.844%	$223.6801	$223.68	$223.70	$223.70
Purchase #2	$205.64	11.543%	$229.377	$229.38	$229.40	$229.40
Purchase #3	$67.32	5.624%	$71.1061	$71.11	$71.10	$71.10
Purchase #4	$243.71	5.339%	$256.7217	$256.72	$256.70	$256.70
Purchase #5	$53.92	4.452%	$56.3205	$56.32	$56.30	$56.30
Purchase #6	$15.56	3.256%	$16.0666	$16.07	$16.05	$16.10
Purchase #7	$111.88	10.640%	$123.784	$123.78	$123.80	$123.80
7 purchase totals =	$909.36		$977.0560	$977.06	$977.05	$977.10