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	$63.69	5.148%	$66.9688	$66.97	$66.95	$67.00
Purchase #2	$150.30	9.707%	$164.8896	$164.89	$164.90	$164.90
Purchase #3	$124.87	6.700%	$133.2363	$133.24	$133.25	$133.20
Purchase #4	$29.54	9.536%	$32.3569	$32.36	$32.35	$32.40
Purchase #5	$195.59	11.826%	$218.7205	$218.72	$218.70	$218.70
Purchase #6	$21.88	9.766%	$24.0168	$24.02	$24.00	$24.00
Purchase #7	$38.44	11.243%	$42.7618	$42.76	$42.75	$42.80
7 purchase totals =	$624.31		$682.9507	$682.96	$682.90	$683.00