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	$202.26	10.263%	$223.0179	$223.02	$223.00	$223.00
Purchase #2	$140.84	8.227%	$152.4269	$152.43	$152.45	$152.40
Purchase #3	$55.34	11.294%	$61.5901	$61.59	$61.60	$61.60
Purchase #4	$142.89	13.169%	$161.7072	$161.71	$161.70	$161.70
Purchase #5	$216.44	3.152%	$223.2622	$223.26	$223.25	$223.30
Purchase #6	$130.40	3.495%	$134.9575	$134.96	$134.95	$135.00
Purchase #7	$94.56	4.145%	$98.4795	$98.48	$98.50	$98.50
7 purchase totals =	$982.73		$1,055.4413	$1,055.45	$1,055.45	$1,055.50