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	$72.34	11.655%	$80.7712	$80.77	$80.75	$80.80
Purchase #2	$95.58	6.205%	$101.5107	$101.51	$101.50	$101.50
Purchase #3	$167.96	13.425%	$190.5086	$190.51	$190.50	$190.50
Purchase #4	$55.85	6.423%	$59.4372	$59.44	$59.45	$59.40
Purchase #5	$78.91	13.398%	$89.4824	$89.48	$89.50	$89.50
Purchase #6	$153.89	5.161%	$161.8323	$161.83	$161.85	$161.80
Purchase #7	$233.84	4.600%	$244.5966	$244.60	$244.60	$244.60
7 purchase totals =	$858.37		$928.1390	$928.14	$928.15	$928.10