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	$58.76	6.363%	$62.4989	$62.50	$62.50	$62.50
Purchase #2	$242.78	5.159%	$255.305	$255.31	$255.30	$255.30
Purchase #3	$179.54	3.758%	$186.2871	$186.29	$186.30	$186.30
Purchase #4	$93.61	6.675%	$99.8585	$99.86	$99.85	$99.90
Purchase #5	$233.67	6.379%	$248.5758	$248.58	$248.60	$248.60
Purchase #6	$36.79	7.123%	$39.4106	$39.41	$39.40	$39.40
Purchase #7	$59.72	7.392%	$64.1345	$64.13	$64.15	$64.10
7 purchase totals =	$904.87		$956.0704	$956.08	$956.10	$956.10