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	$29.79	12.176%	$33.4172	$33.42	$33.40	$33.40
Purchase #2	$29.60	10.657%	$32.7545	$32.75	$32.75	$32.80
Purchase #3	$38.70	12.468%	$43.5251	$43.53	$43.55	$43.50
Purchase #4	$91.39	5.827%	$96.7153	$96.72	$96.70	$96.70
Purchase #5	$245.96	11.127%	$273.328	$273.33	$273.35	$273.30
Purchase #6	$216.89	12.374%	$243.728	$243.73	$243.75	$243.70
Purchase #7	$192.55	9.211%	$210.2858	$210.29	$210.30	$210.30
7 purchase totals =	$844.88		$933.7539	$933.77	$933.80	$933.70