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	$165.88	11.818%	$185.4837	$185.48	$185.50	$185.50
Purchase #2	$227.73	4.131%	$237.1375	$237.14	$237.15	$237.10
Purchase #3	$243.55	8.734%	$264.8217	$264.82	$264.80	$264.80
Purchase #4	$109.53	13.762%	$124.6035	$124.60	$124.60	$124.60
Purchase #5	$19.45	6.433%	$20.7012	$20.70	$20.70	$20.70
Purchase #6	$128.70	10.653%	$142.4104	$142.41	$142.40	$142.40
Purchase #7	$127.97	10.782%	$141.7677	$141.77	$141.75	$141.80
7 purchase totals =	$1,022.81		$1,116.9257	$1,116.92	$1,116.90	$1,116.90