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	$235.98	8.621%	$256.3238	$256.32	$256.30	$256.30
Purchase #2	$32.88	13.746%	$37.3997	$37.40	$37.40	$37.40
Purchase #3	$57.63	3.311%	$59.5381	$59.54	$59.55	$59.50
Purchase #4	$174.73	6.693%	$186.4247	$186.42	$186.40	$186.40
Purchase #5	$11.99	3.300%	$12.3857	$12.39	$12.40	$12.40
Purchase #6	$39.32	5.742%	$41.5778	$41.58	$41.60	$41.60
Purchase #7	$141.98	4.426%	$148.264	$148.26	$148.25	$148.30
7 purchase totals =	$694.51		$741.9138	$741.91	$741.90	$741.90