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	$102.83	8.657%	$111.732	$111.73	$111.75	$111.70
Purchase #2	$200.26	6.253%	$212.7823	$212.78	$212.80	$212.80
Purchase #3	$146.63	10.141%	$161.4997	$161.50	$161.50	$161.50
Purchase #4	$223.33	4.122%	$232.5357	$232.54	$232.55	$232.50
Purchase #5	$137.45	4.658%	$143.8524	$143.85	$143.85	$143.90
Purchase #6	$55.80	7.171%	$59.8014	$59.80	$59.80	$59.80
Purchase #7	$25.44	10.620%	$28.1417	$28.14	$28.15	$28.10
7 purchase totals =	$891.74		$950.3452	$950.34	$950.40	$950.30