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	$146.78	3.858%	$152.4428	$152.44	$152.45	$152.40
Purchase #2	$17.35	4.372%	$18.1085	$18.11	$18.10	$18.10
Purchase #3	$233.73	10.763%	$258.8864	$258.89	$258.90	$258.90
Purchase #4	$28.46	6.586%	$30.3344	$30.33	$30.35	$30.30
Purchase #5	$131.59	9.143%	$143.6213	$143.62	$143.60	$143.60
Purchase #6	$164.74	9.550%	$180.4727	$180.47	$180.45	$180.50
Purchase #7	$42.30	5.405%	$44.5863	$44.59	$44.60	$44.60
7 purchase totals =	$764.95		$828.4524	$828.45	$828.45	$828.40