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	$64.83	7.111%	$69.4401	$69.44	$69.45	$69.40
Purchase #2	$95.40	10.753%	$105.6584	$105.66	$105.65	$105.70
Purchase #3	$198.25	11.773%	$221.59	$221.59	$221.60	$221.60
Purchase #4	$207.45	10.520%	$229.2737	$229.27	$229.25	$229.30
Purchase #5	$25.77	3.169%	$26.5867	$26.59	$26.60	$26.60
Purchase #6	$57.37	4.121%	$59.7342	$59.73	$59.75	$59.70
Purchase #7	$37.69	7.236%	$40.4172	$40.42	$40.40	$40.40
7 purchase totals =	$686.76		$752.7003	$752.70	$752.70	$752.70