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	$245.93	7.814%	$265.147	$265.15	$265.15	$265.10
Purchase #2	$191.38	4.798%	$200.5624	$200.56	$200.55	$200.60
Purchase #3	$141.89	4.636%	$148.468	$148.47	$148.45	$148.50
Purchase #4	$237.52	10.369%	$262.1484	$262.15	$262.15	$262.10
Purchase #5	$16.95	5.678%	$17.9124	$17.91	$17.90	$17.90
Purchase #6	$137.71	7.409%	$147.9129	$147.91	$147.90	$147.90
Purchase #7	$141.58	3.282%	$146.2267	$146.23	$146.25	$146.20
7 purchase totals =	$1,112.96		$1,188.3778	$1,188.38	$1,188.35	$1,188.30