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	$47.76	12.842%	$53.8933	$53.89	$53.90	$53.90
Purchase #2	$143.26	13.720%	$162.9153	$162.92	$162.90	$162.90
Purchase #3	$97.86	7.792%	$105.4853	$105.49	$105.50	$105.50
Purchase #4	$147.71	11.628%	$164.8857	$164.89	$164.90	$164.90
Purchase #5	$50.41	3.488%	$52.1683	$52.17	$52.15	$52.20
Purchase #6	$134.46	10.565%	$148.6657	$148.67	$148.65	$148.70
Purchase #7	$91.74	8.459%	$99.5003	$99.50	$99.50	$99.50
7 purchase totals =	$713.20		$787.5139	$787.53	$787.50	$787.60