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	$67.67	5.540%	$71.4189	$71.42	$71.40	$71.40
Purchase #2	$231.74	10.512%	$256.1005	$256.10	$256.10	$256.10
Purchase #3	$196.52	10.323%	$216.8068	$216.81	$216.80	$216.80
Purchase #4	$216.38	13.187%	$244.914	$244.91	$244.90	$244.90
Purchase #5	$127.75	9.613%	$140.0306	$140.03	$140.05	$140.00
Purchase #6	$96.44	4.578%	$100.855	$100.86	$100.85	$100.90
Purchase #7	$6.33	3.679%	$6.5629	$6.56	$6.55	$6.60
7 purchase totals =	$942.83		$1,036.6887	$1,036.69	$1,036.65	$1,036.70