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	$30.64	9.361%	$33.5082	$33.51	$33.50	$33.50
Purchase #2	$172.63	13.177%	$195.3775	$195.38	$195.40	$195.40
Purchase #3	$99.44	4.130%	$103.5469	$103.55	$103.55	$103.50
Purchase #4	$226.78	3.681%	$235.1278	$235.13	$235.15	$235.10
Purchase #5	$210.89	7.282%	$226.247	$226.25	$226.25	$226.20
Purchase #6	$228.98	7.169%	$245.3956	$245.40	$245.40	$245.40
Purchase #7	$67.33	7.480%	$72.3663	$72.37	$72.35	$72.40
7 purchase totals =	$1,036.69		$1,111.5693	$1,111.59	$1,111.60	$1,111.50