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	$130.36	9.615%	$142.8941	$142.89	$142.90	$142.90
Purchase #2	$25.47	7.756%	$27.4455	$27.45	$27.45	$27.40
Purchase #3	$74.27	11.775%	$83.0153	$83.02	$83.00	$83.00
Purchase #4	$131.82	13.285%	$149.3323	$149.33	$149.35	$149.30
Purchase #5	$149.67	3.711%	$155.2243	$155.22	$155.20	$155.20
Purchase #6	$67.93	12.863%	$76.6678	$76.67	$76.65	$76.70
Purchase #7	$168.49	13.712%	$191.5933	$191.59	$191.60	$191.60
7 purchase totals =	$748.01		$826.1726	$826.17	$826.15	$826.10