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	$46.26	5.376%	$48.7469	$48.75	$48.75	$48.70
Purchase #2	$85.60	6.221%	$90.9252	$90.93	$90.95	$90.90
Purchase #3	$84.71	9.741%	$92.9616	$92.96	$92.95	$93.00
Purchase #4	$168.64	8.137%	$182.3622	$182.36	$182.35	$182.40
Purchase #5	$13.86	5.444%	$14.6145	$14.61	$14.60	$14.60
Purchase #6	$116.97	12.361%	$131.4287	$131.43	$131.45	$131.40
Purchase #7	$37.92	12.671%	$42.7248	$42.72	$42.70	$42.70
7 purchase totals =	$553.96		$603.7639	$603.76	$603.75	$603.70