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	$151.38	10.151%	$166.7466	$166.75	$166.75	$166.70
Purchase #2	$194.57	4.437%	$203.2031	$203.20	$203.20	$203.20
Purchase #3	$136.35	10.113%	$150.1391	$150.14	$150.15	$150.10
Purchase #4	$115.64	10.214%	$127.4515	$127.45	$127.45	$127.50
Purchase #5	$57.40	6.386%	$61.0656	$61.07	$61.05	$61.10
Purchase #6	$56.33	7.447%	$60.5249	$60.52	$60.50	$60.50
Purchase #7	$246.62	9.447%	$269.9182	$269.92	$269.90	$269.90
7 purchase totals =	$958.29		$1,039.0490	$1,039.05	$1,039.00	$1,039.00