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	$236.65	7.243%	$253.7906	$253.79	$253.80	$253.80
Purchase #2	$61.96	13.726%	$70.4646	$70.46	$70.45	$70.50
Purchase #3	$186.51	10.326%	$205.769	$205.77	$205.75	$205.80
Purchase #4	$84.93	6.294%	$90.2755	$90.28	$90.30	$90.30
Purchase #5	$155.58	10.667%	$172.1757	$172.18	$172.20	$172.20
Purchase #6	$36.34	5.300%	$38.266	$38.27	$38.25	$38.30
Purchase #7	$75.71	10.846%	$83.9215	$83.92	$83.90	$83.90
7 purchase totals =	$837.68		$914.6629	$914.67	$914.65	$914.80