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	$211.55	5.587%	$223.3693	$223.37	$223.35	$223.40
Purchase #2	$189.41	11.162%	$210.5519	$210.55	$210.55	$210.60
Purchase #3	$170.77	11.217%	$189.9253	$189.93	$189.95	$189.90
Purchase #4	$177.61	7.457%	$190.8544	$190.85	$190.85	$190.90
Purchase #5	$35.93	11.763%	$40.1564	$40.16	$40.15	$40.20
Purchase #6	$216.67	9.425%	$237.0911	$237.09	$237.10	$237.10
Purchase #7	$55.51	12.272%	$62.3222	$62.32	$62.30	$62.30
7 purchase totals =	$1,057.45		$1,154.2706	$1,154.27	$1,154.25	$1,154.40