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	$38.67	8.213%	$41.846	$41.85	$41.85	$41.80
Purchase #2	$102.59	6.650%	$109.4122	$109.41	$109.40	$109.40
Purchase #3	$184.61	13.303%	$209.1687	$209.17	$209.15	$209.20
Purchase #4	$98.45	13.535%	$111.7752	$111.78	$111.80	$111.80
Purchase #5	$27.46	9.620%	$30.1017	$30.10	$30.10	$30.10
Purchase #6	$195.55	6.704%	$208.6597	$208.66	$208.65	$208.70
Purchase #7	$151.89	13.459%	$172.3329	$172.33	$172.35	$172.30
7 purchase totals =	$799.22		$883.2964	$883.30	$883.30	$883.30