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	$54.88	9.527%	$60.1084	$60.11	$60.10	$60.10
Purchase #2	$120.54	8.790%	$131.1355	$131.14	$131.15	$131.10
Purchase #3	$147.38	13.622%	$167.4561	$167.46	$167.45	$167.50
Purchase #4	$43.45	4.214%	$45.281	$45.28	$45.30	$45.30
Purchase #5	$108.44	9.120%	$118.3297	$118.33	$118.35	$118.30
Purchase #6	$134.44	9.293%	$146.9335	$146.93	$146.95	$146.90
Purchase #7	$11.79	3.186%	$12.1656	$12.17	$12.15	$12.20
7 purchase totals =	$620.92		$681.4098	$681.42	$681.45	$681.40