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	$169.63	9.300%	$185.4056	$185.41	$185.40	$185.40
Purchase #2	$175.85	7.418%	$188.8946	$188.89	$188.90	$188.90
Purchase #3	$149.45	8.414%	$162.0247	$162.02	$162.00	$162.00
Purchase #4	$53.46	4.122%	$55.6636	$55.66	$55.65	$55.70
Purchase #5	$207.35	5.699%	$219.1669	$219.17	$219.15	$219.20
Purchase #6	$180.29	10.145%	$198.5804	$198.58	$198.60	$198.60
Purchase #7	$116.35	12.215%	$130.5622	$130.56	$130.55	$130.60
7 purchase totals =	$1,052.38		$1,140.2980	$1,140.29	$1,140.25	$1,140.40