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	$130.70	8.304%	$141.5533	$141.55	$141.55	$141.60
Purchase #2	$62.34	8.687%	$67.7555	$67.76	$67.75	$67.80
Purchase #3	$68.77	13.833%	$78.283	$78.28	$78.30	$78.30
Purchase #4	$21.75	10.624%	$24.0607	$24.06	$24.05	$24.10
Purchase #5	$81.38	9.362%	$88.9988	$89.00	$89.00	$89.00
Purchase #6	$59.72	4.380%	$62.3357	$62.34	$62.35	$62.30
Purchase #7	$64.76	8.596%	$70.3268	$70.33	$70.35	$70.30
7 purchase totals =	$489.42		$533.3138	$533.32	$533.35	$533.40