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	$28.90	12.869%	$32.6191	$32.62	$32.60	$32.60
Purchase #2	$58.33	5.802%	$61.7143	$61.71	$61.70	$61.70
Purchase #3	$190.47	11.566%	$212.4998	$212.50	$212.50	$212.50
Purchase #4	$153.44	5.314%	$161.5938	$161.59	$161.60	$161.60
Purchase #5	$39.77	3.805%	$41.2832	$41.28	$41.30	$41.30
Purchase #6	$87.58	12.456%	$98.489	$98.49	$98.50	$98.50
Purchase #7	$103.37	10.576%	$114.3024	$114.30	$114.30	$114.30
7 purchase totals =	$661.86		$722.5016	$722.49	$722.50	$722.50