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	$212.28	9.814%	$233.1132	$233.11	$233.10	$233.10
Purchase #2	$131.91	8.295%	$142.8519	$142.85	$142.85	$142.90
Purchase #3	$194.52	9.344%	$212.6959	$212.70	$212.70	$212.70
Purchase #4	$112.50	10.664%	$124.497	$124.50	$124.50	$124.50
Purchase #5	$150.42	10.680%	$166.4849	$166.48	$166.50	$166.50
Purchase #6	$178.77	6.472%	$190.34	$190.34	$190.35	$190.30
Purchase #7	$83.48	5.225%	$87.8418	$87.84	$87.85	$87.80
7 purchase totals =	$1,063.88		$1,157.8247	$1,157.82	$1,157.85	$1,157.80