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	$123.72	5.785%	$130.8772	$130.88	$130.90	$130.90
Purchase #2	$64.55	3.106%	$66.5549	$66.55	$66.55	$66.60
Purchase #3	$40.46	12.693%	$45.5956	$45.60	$45.60	$45.60
Purchase #4	$142.54	12.282%	$160.0468	$160.05	$160.05	$160.00
Purchase #5	$85.68	8.290%	$92.7829	$92.78	$92.80	$92.80
Purchase #6	$154.69	7.128%	$165.7163	$165.72	$165.70	$165.70
Purchase #7	$123.90	9.587%	$135.7783	$135.78	$135.80	$135.80
7 purchase totals =	$735.54		$797.3520	$797.36	$797.40	$797.40