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	$133.36	11.720%	$148.9898	$148.99	$149.00	$149.00
Purchase #2	$40.85	12.477%	$45.9469	$45.95	$45.95	$45.90
Purchase #3	$116.35	12.847%	$131.2975	$131.30	$131.30	$131.30
Purchase #4	$209.32	12.702%	$235.9078	$235.91	$235.90	$235.90
Purchase #5	$247.35	13.258%	$280.1437	$280.14	$280.15	$280.10
Purchase #6	$126.82	4.308%	$132.2834	$132.28	$132.30	$132.30
Purchase #7	$96.77	12.763%	$109.1208	$109.12	$109.10	$109.10
7 purchase totals =	$970.82		$1,083.6899	$1,083.69	$1,083.70	$1,083.60