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	$106.89	4.175%	$111.3527	$111.35	$111.35	$111.40
Purchase #2	$156.35	11.303%	$174.0222	$174.02	$174.00	$174.00
Purchase #3	$146.45	7.601%	$157.5817	$157.58	$157.60	$157.60
Purchase #4	$42.47	3.834%	$44.0983	$44.10	$44.10	$44.10
Purchase #5	$75.69	10.226%	$83.4301	$83.43	$83.45	$83.40
Purchase #6	$91.38	12.321%	$102.6389	$102.64	$102.65	$102.60
Purchase #7	$90.32	3.482%	$93.4649	$93.46	$93.45	$93.50
7 purchase totals =	$709.55		$766.5888	$766.58	$766.60	$766.60