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	$146.31	13.808%	$166.5125	$166.51	$166.50	$166.50
Purchase #2	$206.81	9.786%	$227.0484	$227.05	$227.05	$227.00
Purchase #3	$100.27	11.814%	$112.1159	$112.12	$112.10	$112.10
Purchase #4	$205.38	6.764%	$219.2719	$219.27	$219.25	$219.30
Purchase #5	$164.37	3.199%	$169.6282	$169.63	$169.65	$169.60
Purchase #6	$149.67	12.399%	$168.2276	$168.23	$168.25	$168.20
Purchase #7	$58.42	5.372%	$61.5583	$61.56	$61.55	$61.60
7 purchase totals =	$1,031.23		$1,124.3628	$1,124.37	$1,124.35	$1,124.30