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	$96.91	9.314%	$105.9362	$105.94	$105.95	$105.90
Purchase #2	$127.98	10.705%	$141.6803	$141.68	$141.70	$141.70
Purchase #3	$154.79	7.128%	$165.8234	$165.82	$165.80	$165.80
Purchase #4	$52.31	8.457%	$56.7339	$56.73	$56.75	$56.70
Purchase #5	$75.92	3.313%	$78.4352	$78.44	$78.45	$78.40
Purchase #6	$50.79	4.830%	$53.2432	$53.24	$53.25	$53.20
Purchase #7	$97.26	3.443%	$100.6087	$100.61	$100.60	$100.60
7 purchase totals =	$655.96		$702.4609	$702.46	$702.50	$702.30