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	$229.62	10.831%	$254.4901	$254.49	$254.50	$254.50
Purchase #2	$12.33	11.773%	$13.7816	$13.78	$13.80	$13.80
Purchase #3	$39.28	13.300%	$44.5042	$44.50	$44.50	$44.50
Purchase #4	$149.50	13.780%	$170.1011	$170.10	$170.10	$170.10
Purchase #5	$146.37	6.692%	$156.1651	$156.17	$156.15	$156.20
Purchase #6	$124.34	5.835%	$131.5952	$131.60	$131.60	$131.60
Purchase #7	$136.69	11.473%	$152.3724	$152.37	$152.35	$152.40
7 purchase totals =	$838.13		$923.0097	$923.01	$923.00	$923.10