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	$146.45	4.282%	$152.721	$152.72	$152.70	$152.70
Purchase #2	$32.91	6.695%	$35.1133	$35.11	$35.10	$35.10
Purchase #3	$247.40	13.471%	$280.7273	$280.73	$280.75	$280.70
Purchase #4	$157.58	9.708%	$172.8779	$172.88	$172.90	$172.90
Purchase #5	$126.64	11.510%	$141.2163	$141.22	$141.20	$141.20
Purchase #6	$182.78	8.428%	$198.1847	$198.18	$198.20	$198.20
Purchase #7	$97.69	7.572%	$105.0871	$105.09	$105.10	$105.10
7 purchase totals =	$991.45		$1,085.9276	$1,085.93	$1,085.95	$1,085.90