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	$136.39	8.628%	$148.1577	$148.16	$148.15	$148.20
Purchase #2	$48.97	8.583%	$53.1731	$53.17	$53.15	$53.20
Purchase #3	$179.28	3.361%	$185.3056	$185.31	$185.30	$185.30
Purchase #4	$249.56	9.238%	$272.6144	$272.61	$272.60	$272.60
Purchase #5	$171.43	7.799%	$184.7998	$184.80	$184.80	$184.80
Purchase #6	$166.54	11.852%	$186.2783	$186.28	$186.30	$186.30
Purchase #7	$51.41	5.541%	$54.2586	$54.26	$54.25	$54.30
7 purchase totals =	$1,003.58		$1,084.5875	$1,084.59	$1,084.55	$1,084.70