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	$67.25	13.659%	$76.4357	$76.44	$76.45	$76.40
Purchase #2	$134.97	8.822%	$146.8771	$146.88	$146.90	$146.90
Purchase #3	$130.40	13.419%	$147.8984	$147.90	$147.90	$147.90
Purchase #4	$61.78	5.561%	$65.2156	$65.22	$65.20	$65.20
Purchase #5	$116.29	9.302%	$127.1073	$127.11	$127.10	$127.10
Purchase #6	$100.73	11.565%	$112.3794	$112.38	$112.40	$112.40
Purchase #7	$125.80	8.445%	$136.4238	$136.42	$136.40	$136.40
7 purchase totals =	$737.22		$812.3373	$812.35	$812.35	$812.30