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	$63.52	12.785%	$71.641	$71.64	$71.65	$71.60
Purchase #2	$59.35	9.482%	$64.9776	$64.98	$65.00	$65.00
Purchase #3	$7.58	3.548%	$7.8489	$7.85	$7.85	$7.80
Purchase #4	$189.70	3.728%	$196.772	$196.77	$196.75	$196.80
Purchase #5	$150.51	13.789%	$171.2638	$171.26	$171.25	$171.30
Purchase #6	$118.29	10.153%	$130.3	$130.30	$130.30	$130.30
Purchase #7	$196.88	3.357%	$203.4893	$203.49	$203.50	$203.50
7 purchase totals =	$785.83		$846.2926	$846.29	$846.30	$846.30