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	$171.68	11.568%	$191.5399	$191.54	$191.55	$191.50
Purchase #2	$79.47	12.858%	$89.6883	$89.69	$89.70	$89.70
Purchase #3	$209.44	12.167%	$234.9226	$234.92	$234.90	$234.90
Purchase #4	$190.74	6.429%	$203.0027	$203.00	$203.00	$203.00
Purchase #5	$149.52	11.667%	$166.9645	$166.96	$166.95	$167.00
Purchase #6	$131.89	13.855%	$150.1634	$150.16	$150.15	$150.20
Purchase #7	$38.40	9.864%	$42.1878	$42.19	$42.20	$42.20
7 purchase totals =	$971.14		$1,078.4692	$1,078.46	$1,078.45	$1,078.50