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	$73.61	13.381%	$83.4598	$83.46	$83.45	$83.50
Purchase #2	$120.88	3.787%	$125.4577	$125.46	$125.45	$125.50
Purchase #3	$146.26	3.257%	$151.0237	$151.02	$151.00	$151.00
Purchase #4	$110.25	4.112%	$114.7835	$114.78	$114.80	$114.80
Purchase #5	$220.36	3.740%	$228.6015	$228.60	$228.60	$228.60
Purchase #6	$108.71	8.387%	$117.8275	$117.83	$117.85	$117.80
Purchase #7	$111.89	10.144%	$123.2401	$123.24	$123.25	$123.20
7 purchase totals =	$891.96		$944.3938	$944.39	$944.40	$944.40