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	$222.30	9.486%	$243.3874	$243.39	$243.40	$243.40
Purchase #2	$149.60	11.581%	$166.9252	$166.93	$166.95	$166.90
Purchase #3	$10.66	11.843%	$11.9225	$11.92	$11.90	$11.90
Purchase #4	$209.31	4.612%	$218.9634	$218.96	$218.95	$219.00
Purchase #5	$39.52	4.640%	$41.3537	$41.35	$41.35	$41.40
Purchase #6	$172.65	5.285%	$181.7746	$181.77	$181.75	$181.80
Purchase #7	$201.71	10.666%	$223.2244	$223.22	$223.20	$223.20
7 purchase totals =	$1,005.75		$1,087.5512	$1,087.54	$1,087.50	$1,087.60