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	$100.52	12.117%	$112.7	$112.70	$112.70	$112.70
Purchase #2	$116.38	3.372%	$120.3043	$120.30	$120.30	$120.30
Purchase #3	$184.50	13.347%	$209.1252	$209.13	$209.15	$209.10
Purchase #4	$112.58	10.497%	$124.3975	$124.40	$124.40	$124.40
Purchase #5	$161.74	12.111%	$181.3283	$181.33	$181.35	$181.30
Purchase #6	$99.53	5.848%	$105.3505	$105.35	$105.35	$105.40
Purchase #7	$144.92	13.311%	$164.2103	$164.21	$164.20	$164.20
7 purchase totals =	$920.17		$1,017.4161	$1,017.42	$1,017.45	$1,017.40