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	$130.40	4.610%	$136.4114	$136.41	$136.40	$136.40
Purchase #2	$237.46	6.154%	$252.0733	$252.07	$252.05	$252.10
Purchase #3	$80.81	12.401%	$90.8312	$90.83	$90.85	$90.80
Purchase #4	$37.32	7.446%	$40.0988	$40.10	$40.10	$40.10
Purchase #5	$207.86	6.851%	$222.1005	$222.10	$222.10	$222.10
Purchase #6	$247.58	10.557%	$273.717	$273.72	$273.70	$273.70
Purchase #7	$133.70	13.150%	$151.2816	$151.28	$151.30	$151.30
7 purchase totals =	$1,075.13		$1,166.5138	$1,166.51	$1,166.50	$1,166.50