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	$127.45	3.105%	$131.4073	$131.41	$131.40	$131.40
Purchase #2	$192.70	10.127%	$212.2147	$212.21	$212.20	$212.20
Purchase #3	$162.76	5.429%	$171.5962	$171.60	$171.60	$171.60
Purchase #4	$148.55	3.543%	$153.8131	$153.81	$153.80	$153.80
Purchase #5	$36.26	3.530%	$37.54	$37.54	$37.55	$37.50
Purchase #6	$89.27	12.790%	$100.6876	$100.69	$100.70	$100.70
Purchase #7	$99.44	10.257%	$109.6396	$109.64	$109.65	$109.60
7 purchase totals =	$856.43		$916.8985	$916.90	$916.90	$916.80