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	$10.49	12.673%	$11.8194	$11.82	$11.80	$11.80
Purchase #2	$11.77	11.492%	$13.1226	$13.12	$13.10	$13.10
Purchase #3	$207.57	7.809%	$223.7791	$223.78	$223.80	$223.80
Purchase #4	$178.88	6.270%	$190.0958	$190.10	$190.10	$190.10
Purchase #5	$157.33	11.748%	$175.8131	$175.81	$175.80	$175.80
Purchase #6	$220.39	5.801%	$233.1748	$233.17	$233.15	$233.20
Purchase #7	$116.83	8.835%	$127.1519	$127.15	$127.15	$127.20
7 purchase totals =	$903.26		$974.9567	$974.95	$974.90	$975.00