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	$201.55	6.800%	$215.2554	$215.26	$215.25	$215.30
Purchase #2	$135.61	9.521%	$148.5214	$148.52	$148.50	$148.50
Purchase #3	$53.38	11.705%	$59.6281	$59.63	$59.65	$59.60
Purchase #4	$197.53	11.119%	$219.4934	$219.49	$219.50	$219.50
Purchase #5	$124.73	10.456%	$137.7718	$137.77	$137.75	$137.80
Purchase #6	$16.27	5.700%	$17.1974	$17.20	$17.20	$17.20
Purchase #7	$168.65	7.122%	$180.6613	$180.66	$180.65	$180.70
7 purchase totals =	$897.72		$978.5288	$978.53	$978.50	$978.60