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	$116.90	12.636%	$131.6715	$131.67	$131.65	$131.70
Purchase #2	$150.83	3.586%	$156.2388	$156.24	$156.25	$156.20
Purchase #3	$63.32	3.350%	$65.4412	$65.44	$65.45	$65.40
Purchase #4	$29.69	12.149%	$33.297	$33.30	$33.30	$33.30
Purchase #5	$35.47	9.197%	$38.7322	$38.73	$38.75	$38.70
Purchase #6	$178.86	12.196%	$200.6738	$200.67	$200.65	$200.70
Purchase #7	$127.28	4.578%	$133.1069	$133.11	$133.10	$133.10
7 purchase totals =	$702.35		$759.1614	$759.16	$759.15	$759.10