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	$196.89	11.189%	$218.92	$218.92	$218.90	$218.90
Purchase #2	$113.90	6.696%	$121.5267	$121.53	$121.55	$121.50
Purchase #3	$99.88	10.325%	$110.1926	$110.19	$110.20	$110.20
Purchase #4	$16.85	13.507%	$19.1259	$19.13	$19.15	$19.10
Purchase #5	$106.80	4.228%	$111.3155	$111.32	$111.30	$111.30
Purchase #6	$53.37	13.600%	$60.6283	$60.63	$60.65	$60.60
Purchase #7	$82.82	10.593%	$91.5931	$91.59	$91.60	$91.60
7 purchase totals =	$670.51		$733.3021	$733.31	$733.35	$733.20