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	$210.63	7.808%	$227.076	$227.08	$227.10	$227.10
Purchase #2	$209.43	12.799%	$236.2349	$236.23	$236.25	$236.20
Purchase #3	$83.25	7.576%	$89.557	$89.56	$89.55	$89.60
Purchase #4	$149.80	11.291%	$166.7139	$166.71	$166.70	$166.70
Purchase #5	$40.88	4.248%	$42.6166	$42.62	$42.60	$42.60
Purchase #6	$66.35	13.608%	$75.3789	$75.38	$75.40	$75.40
Purchase #7	$172.39	5.768%	$182.3335	$182.33	$182.35	$182.30
7 purchase totals =	$932.73		$1,019.9108	$1,019.91	$1,019.95	$1,019.90