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	$64.35	12.732%	$72.543	$72.54	$72.55	$72.50
Purchase #2	$54.69	10.532%	$60.45	$60.45	$60.45	$60.50
Purchase #3	$195.31	9.106%	$213.0949	$213.09	$213.10	$213.10
Purchase #4	$156.27	11.712%	$174.5723	$174.57	$174.55	$174.60
Purchase #5	$209.64	13.299%	$237.52	$237.52	$237.50	$237.50
Purchase #6	$88.43	9.359%	$96.7062	$96.71	$96.70	$96.70
Purchase #7	$79.85	4.842%	$83.7163	$83.72	$83.70	$83.70
7 purchase totals =	$848.54		$938.6027	$938.60	$938.55	$938.60