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	$146.36	4.118%	$152.3871	$152.39	$152.40	$152.40
Purchase #2	$51.82	5.504%	$54.6722	$54.67	$54.65	$54.70
Purchase #3	$82.61	10.355%	$91.1643	$91.16	$91.15	$91.20
Purchase #4	$20.82	4.677%	$21.7938	$21.79	$21.80	$21.80
Purchase #5	$33.61	11.830%	$37.5861	$37.59	$37.60	$37.60
Purchase #6	$25.95	4.785%	$27.1917	$27.19	$27.20	$27.20
Purchase #7	$179.48	10.361%	$198.0759	$198.08	$198.10	$198.10
7 purchase totals =	$540.65		$582.8711	$582.87	$582.90	$583.00