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	$242.51	5.629%	$256.1609	$256.16	$256.15	$256.20
Purchase #2	$86.56	12.674%	$97.5306	$97.53	$97.55	$97.50
Purchase #3	$147.59	13.345%	$167.2859	$167.29	$167.30	$167.30
Purchase #4	$142.75	3.786%	$148.1545	$148.15	$148.15	$148.20
Purchase #5	$172.73	4.126%	$179.8568	$179.86	$179.85	$179.90
Purchase #6	$82.39	4.759%	$86.3109	$86.31	$86.30	$86.30
Purchase #7	$202.79	5.834%	$214.6208	$214.62	$214.60	$214.60
7 purchase totals =	$1,077.32		$1,149.9204	$1,149.92	$1,149.90	$1,150.00