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	$50.58	9.295%	$55.2814	$55.28	$55.30	$55.30
Purchase #2	$196.72	5.372%	$207.2878	$207.29	$207.30	$207.30
Purchase #3	$78.59	4.629%	$82.2279	$82.23	$82.25	$82.20
Purchase #4	$115.28	13.298%	$130.6099	$130.61	$130.60	$130.60
Purchase #5	$221.78	4.569%	$231.9131	$231.91	$231.90	$231.90
Purchase #6	$219.32	11.428%	$244.3839	$244.38	$244.40	$244.40
Purchase #7	$130.70	7.514%	$140.5208	$140.52	$140.50	$140.50
7 purchase totals =	$1,012.97		$1,092.2248	$1,092.22	$1,092.25	$1,092.20