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	$196.29	3.831%	$203.8099	$203.81	$203.80	$203.80
Purchase #2	$35.56	5.777%	$37.6143	$37.61	$37.60	$37.60
Purchase #3	$76.63	6.118%	$81.3182	$81.32	$81.30	$81.30
Purchase #4	$156.37	10.218%	$172.3479	$172.35	$172.35	$172.30
Purchase #5	$155.90	12.190%	$174.9042	$174.90	$174.90	$174.90
Purchase #6	$50.30	11.361%	$56.0146	$56.01	$56.00	$56.00
Purchase #7	$248.57	9.113%	$271.2222	$271.22	$271.20	$271.20
7 purchase totals =	$919.62		$997.2313	$997.22	$997.15	$997.10