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	$30.55	13.544%	$34.6877	$34.69	$34.70	$34.70
Purchase #2	$149.93	13.131%	$169.6173	$169.62	$169.60	$169.60
Purchase #3	$243.79	11.674%	$272.25	$272.25	$272.25	$272.30
Purchase #4	$185.48	13.519%	$210.555	$210.56	$210.55	$210.60
Purchase #5	$136.67	6.413%	$145.4346	$145.43	$145.45	$145.40
Purchase #6	$152.43	3.640%	$157.9785	$157.98	$158.00	$158.00
Purchase #7	$183.95	12.123%	$206.2503	$206.25	$206.25	$206.30
7 purchase totals =	$1,082.80		$1,196.7734	$1,196.78	$1,196.80	$1,196.90