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	$92.55	10.481%	$102.2502	$102.25	$102.25	$102.30
Purchase #2	$130.41	5.564%	$137.666	$137.67	$137.65	$137.70
Purchase #3	$111.86	13.785%	$127.2799	$127.28	$127.30	$127.30
Purchase #4	$46.52	4.620%	$48.6692	$48.67	$48.65	$48.70
Purchase #5	$38.68	9.339%	$42.2923	$42.29	$42.30	$42.30
Purchase #6	$193.43	13.122%	$218.8119	$218.81	$218.80	$218.80
Purchase #7	$188.89	7.639%	$203.3193	$203.32	$203.30	$203.30
7 purchase totals =	$802.34		$880.2888	$880.29	$880.25	$880.40