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	$171.82	11.638%	$191.8164	$191.82	$191.80	$191.80
Purchase #2	$247.97	8.542%	$269.1516	$269.15	$269.15	$269.20
Purchase #3	$131.94	13.407%	$149.6292	$149.63	$149.65	$149.60
Purchase #4	$76.99	7.640%	$82.872	$82.87	$82.85	$82.90
Purchase #5	$141.44	7.621%	$152.2191	$152.22	$152.20	$152.20
Purchase #6	$211.50	10.195%	$233.0624	$233.06	$233.05	$233.10
Purchase #7	$55.88	9.431%	$61.15	$61.15	$61.15	$61.20
7 purchase totals =	$1,037.54		$1,139.9007	$1,139.90	$1,139.85	$1,140.00