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	$67.43	7.538%	$72.5129	$72.51	$72.50	$72.50
Purchase #2	$145.54	6.347%	$154.7774	$154.78	$154.80	$154.80
Purchase #3	$245.88	3.258%	$253.8908	$253.89	$253.90	$253.90
Purchase #4	$140.65	4.564%	$147.0693	$147.07	$147.05	$147.10
Purchase #5	$210.97	10.486%	$233.0923	$233.09	$233.10	$233.10
Purchase #6	$234.47	10.276%	$258.5641	$258.56	$258.55	$258.60
Purchase #7	$12.82	13.765%	$14.5847	$14.58	$14.60	$14.60
7 purchase totals =	$1,057.76		$1,134.4915	$1,134.48	$1,134.50	$1,134.60