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	$153.71	9.415%	$168.1818	$168.18	$168.20	$168.20
Purchase #2	$177.65	6.564%	$189.3109	$189.31	$189.30	$189.30
Purchase #3	$140.39	4.300%	$146.4268	$146.43	$146.45	$146.40
Purchase #4	$44.63	12.533%	$50.2235	$50.22	$50.20	$50.20
Purchase #5	$191.74	13.747%	$218.0985	$218.10	$218.10	$218.10
Purchase #6	$146.42	6.204%	$155.5039	$155.50	$155.50	$155.50
Purchase #7	$250.25	7.210%	$268.293	$268.29	$268.30	$268.30
7 purchase totals =	$1,104.79		$1,196.0384	$1,196.03	$1,196.05	$1,196.00