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	$67.72	5.180%	$71.2279	$71.23	$71.25	$71.20
Purchase #2	$241.73	13.196%	$273.6287	$273.63	$273.65	$273.60
Purchase #3	$126.25	5.817%	$133.594	$133.59	$133.60	$133.60
Purchase #4	$185.83	12.492%	$209.0439	$209.04	$209.05	$209.00
Purchase #5	$145.57	4.834%	$152.6069	$152.61	$152.60	$152.60
Purchase #6	$184.28	4.775%	$193.0794	$193.08	$193.10	$193.10
Purchase #7	$120.59	10.264%	$132.9674	$132.97	$132.95	$133.00
7 purchase totals =	$1,071.97		$1,166.1482	$1,166.15	$1,166.20	$1,166.10