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	$185.83	13.188%	$210.3373	$210.34	$210.35	$210.30
Purchase #2	$77.42	10.488%	$85.5398	$85.54	$85.55	$85.50
Purchase #3	$213.77	4.450%	$223.2828	$223.28	$223.30	$223.30
Purchase #4	$30.27	5.263%	$31.8631	$31.86	$31.85	$31.90
Purchase #5	$239.87	13.825%	$273.032	$273.03	$273.05	$273.00
Purchase #6	$136.36	4.557%	$142.5739	$142.57	$142.55	$142.60
Purchase #7	$229.55	8.343%	$248.7014	$248.70	$248.70	$248.70
7 purchase totals =	$1,113.07		$1,215.3303	$1,215.32	$1,215.35	$1,215.30