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	$146.53	5.815%	$155.0507	$155.05	$155.05	$155.10
Purchase #2	$30.30	11.505%	$33.786	$33.79	$33.80	$33.80
Purchase #3	$52.72	9.107%	$57.5212	$57.52	$57.50	$57.50
Purchase #4	$128.25	11.855%	$143.454	$143.45	$143.45	$143.50
Purchase #5	$229.62	10.789%	$254.3937	$254.39	$254.40	$254.40
Purchase #6	$39.99	8.619%	$43.4367	$43.44	$43.45	$43.40
Purchase #7	$122.96	9.419%	$134.5416	$134.54	$134.55	$134.50
7 purchase totals =	$750.37		$822.1839	$822.18	$822.20	$822.20