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	$163.80	13.483%	$185.8852	$185.89	$185.90	$185.90
Purchase #2	$172.85	10.679%	$191.3087	$191.31	$191.30	$191.30
Purchase #3	$80.31	6.670%	$85.6667	$85.67	$85.65	$85.70
Purchase #4	$105.53	11.563%	$117.7324	$117.73	$117.75	$117.70
Purchase #5	$62.90	13.723%	$71.5318	$71.53	$71.55	$71.50
Purchase #6	$158.61	12.851%	$178.993	$178.99	$179.00	$179.00
Purchase #7	$210.57	12.748%	$237.4135	$237.41	$237.40	$237.40
7 purchase totals =	$954.57		$1,068.5313	$1,068.53	$1,068.55	$1,068.50