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	$186.54	7.124%	$199.8291	$199.83	$199.85	$199.80
Purchase #2	$162.47	11.502%	$181.1573	$181.16	$181.15	$181.20
Purchase #3	$140.78	6.677%	$150.1799	$150.18	$150.20	$150.20
Purchase #4	$116.89	6.134%	$124.06	$124.06	$124.05	$124.10
Purchase #5	$100.60	4.678%	$105.3061	$105.31	$105.30	$105.30
Purchase #6	$16.48	5.519%	$17.3895	$17.39	$17.40	$17.40
Purchase #7	$28.39	13.256%	$32.1534	$32.15	$32.15	$32.20
7 purchase totals =	$752.15		$810.0753	$810.08	$810.10	$810.20