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	$71.46	3.385%	$73.8789	$73.88	$73.90	$73.90
Purchase #2	$234.93	8.850%	$255.7213	$255.72	$255.70	$255.70
Purchase #3	$195.73	13.640%	$222.4276	$222.43	$222.45	$222.40
Purchase #4	$172.39	4.400%	$179.9752	$179.98	$180.00	$180.00
Purchase #5	$64.32	3.142%	$66.3409	$66.34	$66.35	$66.30
Purchase #6	$201.78	10.791%	$223.5541	$223.55	$223.55	$223.60
Purchase #7	$132.90	5.365%	$140.0301	$140.03	$140.05	$140.00
7 purchase totals =	$1,073.51		$1,161.9281	$1,161.93	$1,162.00	$1,161.90