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	$218.38	9.109%	$238.2722	$238.27	$238.25	$238.30
Purchase #2	$138.41	9.502%	$151.5617	$151.56	$151.55	$151.60
Purchase #3	$40.71	6.377%	$43.3061	$43.31	$43.30	$43.30
Purchase #4	$54.48	12.173%	$61.1119	$61.11	$61.10	$61.10
Purchase #5	$181.56	4.634%	$189.9735	$189.97	$189.95	$190.00
Purchase #6	$160.93	10.191%	$177.3304	$177.33	$177.35	$177.30
Purchase #7	$114.54	6.151%	$121.5854	$121.59	$121.60	$121.60
7 purchase totals =	$909.01		$983.1412	$983.14	$983.10	$983.20