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	$121.42	9.772%	$133.2852	$133.29	$133.30	$133.30
Purchase #2	$174.72	5.749%	$184.7647	$184.76	$184.75	$184.80
Purchase #3	$122.44	7.269%	$131.3402	$131.34	$131.35	$131.30
Purchase #4	$175.31	7.413%	$188.3057	$188.31	$188.30	$188.30
Purchase #5	$152.52	10.815%	$169.015	$169.02	$169.00	$169.00
Purchase #6	$140.76	13.124%	$159.2333	$159.23	$159.25	$159.20
Purchase #7	$153.88	5.695%	$162.6435	$162.64	$162.65	$162.60
7 purchase totals =	$1,041.05		$1,128.5876	$1,128.59	$1,128.60	$1,128.50