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	$191.72	12.103%	$214.9239	$214.92	$214.90	$214.90
Purchase #2	$90.26	4.801%	$94.5934	$94.59	$94.60	$94.60
Purchase #3	$142.32	6.784%	$151.975	$151.98	$152.00	$152.00
Purchase #4	$71.40	9.513%	$78.1923	$78.19	$78.20	$78.20
Purchase #5	$161.96	10.112%	$178.3374	$178.34	$178.35	$178.30
Purchase #6	$39.84	10.872%	$44.1714	$44.17	$44.15	$44.20
Purchase #7	$141.53	10.560%	$156.4756	$156.48	$156.50	$156.50
7 purchase totals =	$839.03		$918.6690	$918.67	$918.70	$918.70