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	$175.36	13.565%	$199.1476	$199.15	$199.15	$199.10
Purchase #2	$204.28	13.243%	$231.3328	$231.33	$231.35	$231.30
Purchase #3	$64.30	10.819%	$71.2566	$71.26	$71.25	$71.30
Purchase #4	$85.92	7.856%	$92.6699	$92.67	$92.65	$92.70
Purchase #5	$163.92	11.349%	$182.5233	$182.52	$182.50	$182.50
Purchase #6	$213.48	11.734%	$238.5297	$238.53	$238.55	$238.50
Purchase #7	$137.80	10.755%	$152.6204	$152.62	$152.60	$152.60
7 purchase totals =	$1,045.06		$1,168.0803	$1,168.08	$1,168.05	$1,168.00