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	$105.34	10.406%	$116.3017	$116.30	$116.30	$116.30
Purchase #2	$125.55	4.174%	$130.7905	$130.79	$130.80	$130.80
Purchase #3	$213.39	7.469%	$229.3281	$229.33	$229.35	$229.30
Purchase #4	$111.94	9.302%	$122.3527	$122.35	$122.35	$122.40
Purchase #5	$207.71	7.231%	$222.7295	$222.73	$222.75	$222.70
Purchase #6	$93.67	6.333%	$99.6021	$99.60	$99.60	$99.60
Purchase #7	$187.78	4.405%	$196.0517	$196.05	$196.05	$196.10
7 purchase totals =	$1,045.38		$1,117.1563	$1,117.15	$1,117.20	$1,117.20