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	$196.53	5.862%	$208.0506	$208.05	$208.05	$208.10
Purchase #2	$25.74	4.471%	$26.8908	$26.89	$26.90	$26.90
Purchase #3	$134.81	9.468%	$147.5738	$147.57	$147.55	$147.60
Purchase #4	$169.70	7.756%	$182.8619	$182.86	$182.85	$182.90
Purchase #5	$103.68	5.686%	$109.5752	$109.58	$109.60	$109.60
Purchase #6	$114.25	11.308%	$127.1694	$127.17	$127.15	$127.20
Purchase #7	$70.63	10.660%	$78.1592	$78.16	$78.15	$78.20
7 purchase totals =	$815.34		$880.2809	$880.28	$880.25	$880.50