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	$191.60	4.157%	$199.5648	$199.56	$199.55	$199.60
Purchase #2	$53.71	11.297%	$59.7776	$59.78	$59.80	$59.80
Purchase #3	$39.71	4.628%	$41.5478	$41.55	$41.55	$41.50
Purchase #4	$123.72	4.735%	$129.5781	$129.58	$129.60	$129.60
Purchase #5	$167.39	10.163%	$184.4018	$184.40	$184.40	$184.40
Purchase #6	$85.52	3.550%	$88.556	$88.56	$88.55	$88.60
Purchase #7	$116.33	3.564%	$120.476	$120.48	$120.50	$120.50
7 purchase totals =	$777.98		$823.9021	$823.91	$823.95	$824.00