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	$48.56	9.461%	$53.1543	$53.15	$53.15	$53.20
Purchase #2	$137.51	10.623%	$152.1177	$152.12	$152.10	$152.10
Purchase #3	$191.39	9.386%	$209.3539	$209.35	$209.35	$209.40
Purchase #4	$21.89	8.228%	$23.6911	$23.69	$23.70	$23.70
Purchase #5	$131.92	9.554%	$144.5236	$144.52	$144.50	$144.50
Purchase #6	$142.83	5.640%	$150.8856	$150.89	$150.90	$150.90
Purchase #7	$162.85	8.359%	$176.4626	$176.46	$176.45	$176.50
7 purchase totals =	$836.95		$910.1888	$910.18	$910.15	$910.30