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	$206.59	3.385%	$213.5831	$213.58	$213.60	$213.60
Purchase #2	$207.69	4.315%	$216.6518	$216.65	$216.65	$216.70
Purchase #3	$55.57	12.614%	$62.5796	$62.58	$62.60	$62.60
Purchase #4	$53.89	11.507%	$60.0911	$60.09	$60.10	$60.10
Purchase #5	$141.73	6.597%	$151.0799	$151.08	$151.10	$151.10
Purchase #6	$159.35	8.469%	$172.8454	$172.85	$172.85	$172.80
Purchase #7	$205.33	3.690%	$212.9067	$212.91	$212.90	$212.90
7 purchase totals =	$1,030.15		$1,089.7376	$1,089.74	$1,089.80	$1,089.80