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	$169.33	7.212%	$181.5421	$181.54	$181.55	$181.50
Purchase #2	$16.74	9.708%	$18.3651	$18.37	$18.35	$18.40
Purchase #3	$220.54	12.573%	$248.2685	$248.27	$248.25	$248.30
Purchase #4	$169.55	13.186%	$191.9069	$191.91	$191.90	$191.90
Purchase #5	$72.72	12.586%	$81.8725	$81.87	$81.85	$81.90
Purchase #6	$192.59	11.386%	$214.5183	$214.52	$214.50	$214.50
Purchase #7	$165.98	4.732%	$173.8342	$173.83	$173.85	$173.80
7 purchase totals =	$1,007.45		$1,110.3076	$1,110.31	$1,110.25	$1,110.30