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	$75.96	7.123%	$81.3706	$81.37	$81.35	$81.40
Purchase #2	$177.73	10.773%	$196.8769	$196.88	$196.90	$196.90
Purchase #3	$249.98	6.728%	$266.7987	$266.80	$266.80	$266.80
Purchase #4	$135.39	9.235%	$147.8933	$147.89	$147.90	$147.90
Purchase #5	$38.63	10.502%	$42.6869	$42.69	$42.70	$42.70
Purchase #6	$28.96	10.747%	$32.0723	$32.07	$32.05	$32.10
Purchase #7	$221.84	13.480%	$251.744	$251.74	$251.75	$251.70
7 purchase totals =	$928.49		$1,019.4427	$1,019.44	$1,019.45	$1,019.50