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	$153.87	7.330%	$165.1487	$165.15	$165.15	$165.10
Purchase #2	$206.82	4.272%	$215.6554	$215.66	$215.65	$215.70
Purchase #3	$64.90	9.549%	$71.0973	$71.10	$71.10	$71.10
Purchase #4	$37.94	13.637%	$43.1139	$43.11	$43.10	$43.10
Purchase #5	$21.68	10.375%	$23.9293	$23.93	$23.95	$23.90
Purchase #6	$153.25	8.842%	$166.8004	$166.80	$166.80	$166.80
Purchase #7	$104.91	6.156%	$111.3683	$111.37	$111.35	$111.40
7 purchase totals =	$743.37		$797.1133	$797.12	$797.10	$797.10