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	$55.96	11.311%	$62.2896	$62.29	$62.30	$62.30
Purchase #2	$61.52	7.119%	$65.8996	$65.90	$65.90	$65.90
Purchase #3	$40.74	12.311%	$45.7555	$45.76	$45.75	$45.80
Purchase #4	$42.68	13.405%	$48.4013	$48.40	$48.40	$48.40
Purchase #5	$76.47	11.305%	$85.1149	$85.11	$85.10	$85.10
Purchase #6	$170.80	3.737%	$177.1828	$177.18	$177.20	$177.20
Purchase #7	$41.33	9.444%	$45.2332	$45.23	$45.25	$45.20
7 purchase totals =	$489.50		$529.8769	$529.87	$529.90	$529.90