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	$202.87	5.741%	$214.5168	$214.52	$214.50	$214.50
Purchase #2	$212.69	4.531%	$222.327	$222.33	$222.35	$222.30
Purchase #3	$74.55	7.677%	$80.2732	$80.27	$80.25	$80.30
Purchase #4	$180.42	6.178%	$191.5663	$191.57	$191.55	$191.60
Purchase #5	$139.83	12.394%	$157.1605	$157.16	$157.15	$157.20
Purchase #6	$39.27	4.717%	$41.1224	$41.12	$41.10	$41.10
Purchase #7	$77.70	6.295%	$82.5912	$82.59	$82.60	$82.60
7 purchase totals =	$927.33		$989.5574	$989.56	$989.50	$989.60