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	$68.69	5.723%	$72.6211	$72.62	$72.60	$72.60
Purchase #2	$183.77	9.179%	$200.6382	$200.64	$200.65	$200.60
Purchase #3	$221.64	5.696%	$234.2646	$234.26	$234.25	$234.30
Purchase #4	$38.31	13.738%	$43.573	$43.57	$43.55	$43.60
Purchase #5	$90.86	9.842%	$99.8024	$99.80	$99.80	$99.80
Purchase #6	$80.58	11.107%	$89.53	$89.53	$89.55	$89.50
Purchase #7	$69.69	7.852%	$75.1621	$75.16	$75.15	$75.20
7 purchase totals =	$753.54		$815.5914	$815.58	$815.55	$815.60