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	$141.73	4.796%	$148.5274	$148.53	$148.55	$148.50
Purchase #2	$89.66	13.570%	$101.8269	$101.83	$101.85	$101.80
Purchase #3	$94.43	9.444%	$103.348	$103.35	$103.35	$103.30
Purchase #4	$103.39	11.408%	$115.1847	$115.18	$115.20	$115.20
Purchase #5	$165.86	12.546%	$186.6688	$186.67	$186.65	$186.70
Purchase #6	$41.83	9.329%	$45.7323	$45.73	$45.75	$45.70
Purchase #7	$184.92	3.622%	$191.6178	$191.62	$191.60	$191.60
7 purchase totals =	$821.82		$892.9059	$892.91	$892.95	$892.80