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	$200.83	8.781%	$218.4649	$218.46	$218.45	$218.50
Purchase #2	$157.73	4.778%	$165.2663	$165.27	$165.25	$165.30
Purchase #3	$137.34	4.659%	$143.7387	$143.74	$143.75	$143.70
Purchase #4	$54.86	12.847%	$61.9079	$61.91	$61.90	$61.90
Purchase #5	$198.53	9.624%	$217.6365	$217.64	$217.65	$217.60
Purchase #6	$169.71	6.241%	$180.3016	$180.30	$180.30	$180.30
Purchase #7	$68.92	4.282%	$71.8712	$71.87	$71.85	$71.90
7 purchase totals =	$987.92		$1,059.1871	$1,059.19	$1,059.15	$1,059.20