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	$161.60	6.114%	$171.4802	$171.48	$171.50	$171.50
Purchase #2	$56.40	10.112%	$62.1032	$62.10	$62.10	$62.10
Purchase #3	$10.85	11.684%	$12.1177	$12.12	$12.10	$12.10
Purchase #4	$31.78	9.576%	$34.8233	$34.82	$34.80	$34.80
Purchase #5	$164.41	5.460%	$173.3868	$173.39	$173.40	$173.40
Purchase #6	$86.66	5.619%	$91.5294	$91.53	$91.55	$91.50
Purchase #7	$235.44	3.565%	$243.8334	$243.83	$243.85	$243.80
7 purchase totals =	$747.14		$789.2740	$789.27	$789.30	$789.20