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	$75.30	13.209%	$85.2464	$85.25	$85.25	$85.20
Purchase #2	$15.33	3.714%	$15.8994	$15.90	$15.90	$15.90
Purchase #3	$186.75	9.398%	$204.3008	$204.30	$204.30	$204.30
Purchase #4	$239.57	10.446%	$264.5955	$264.60	$264.60	$264.60
Purchase #5	$30.26	11.105%	$33.6204	$33.62	$33.60	$33.60
Purchase #6	$209.38	9.288%	$228.8272	$228.83	$228.85	$228.80
Purchase #7	$62.68	4.232%	$65.3326	$65.33	$65.35	$65.30
7 purchase totals =	$819.27		$897.8223	$897.83	$897.85	$897.70