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	$212.61	5.149%	$223.5573	$223.56	$223.55	$223.60
Purchase #2	$130.82	10.291%	$144.2827	$144.28	$144.30	$144.30
Purchase #3	$161.87	6.797%	$172.8723	$172.87	$172.85	$172.90
Purchase #4	$233.61	10.767%	$258.7628	$258.76	$258.75	$258.80
Purchase #5	$38.70	9.412%	$42.3424	$42.34	$42.35	$42.30
Purchase #6	$177.53	13.383%	$201.2888	$201.29	$201.30	$201.30
Purchase #7	$124.64	4.171%	$129.8387	$129.84	$129.85	$129.80
7 purchase totals =	$1,079.78		$1,172.9450	$1,172.94	$1,172.95	$1,173.00