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	$75.91	3.213%	$78.349	$78.35	$78.35	$78.30
Purchase #2	$146.96	3.304%	$151.8156	$151.82	$151.80	$151.80
Purchase #3	$192.66	5.560%	$203.3719	$203.37	$203.35	$203.40
Purchase #4	$118.39	4.555%	$123.7827	$123.78	$123.80	$123.80
Purchase #5	$172.48	10.202%	$190.0764	$190.08	$190.10	$190.10
Purchase #6	$45.48	6.577%	$48.4712	$48.47	$48.45	$48.50
Purchase #7	$248.87	7.228%	$266.8583	$266.86	$266.85	$266.90
7 purchase totals =	$1,000.75		$1,062.7251	$1,062.73	$1,062.70	$1,062.80