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	$57.52	3.583%	$59.5809	$59.58	$59.60	$59.60
Purchase #2	$39.39	8.144%	$42.5979	$42.60	$42.60	$42.60
Purchase #3	$13.79	6.750%	$14.7208	$14.72	$14.70	$14.70
Purchase #4	$64.50	12.231%	$72.389	$72.39	$72.40	$72.40
Purchase #5	$193.34	6.575%	$206.0521	$206.05	$206.05	$206.10
Purchase #6	$6.98	4.865%	$7.3196	$7.32	$7.30	$7.30
Purchase #7	$216.61	7.143%	$232.0825	$232.08	$232.10	$232.10
7 purchase totals =	$592.13		$634.7428	$634.74	$634.75	$634.80