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	$57.76	7.846%	$62.2918	$62.29	$62.30	$62.30
Purchase #2	$98.61	13.339%	$111.7636	$111.76	$111.75	$111.80
Purchase #3	$37.69	7.869%	$40.6558	$40.66	$40.65	$40.70
Purchase #4	$134.53	5.145%	$141.4516	$141.45	$141.45	$141.50
Purchase #5	$87.57	13.112%	$99.0522	$99.05	$99.05	$99.10
Purchase #6	$207.62	8.869%	$226.0338	$226.03	$226.05	$226.00
Purchase #7	$202.98	12.642%	$228.6407	$228.64	$228.65	$228.60
7 purchase totals =	$826.76		$909.8895	$909.88	$909.90	$910.00