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	$184.51	6.473%	$196.4533	$196.45	$196.45	$196.50
Purchase #2	$217.44	10.836%	$241.0018	$241.00	$241.00	$241.00
Purchase #3	$249.33	11.727%	$278.5689	$278.57	$278.55	$278.60
Purchase #4	$45.44	9.181%	$49.6118	$49.61	$49.60	$49.60
Purchase #5	$62.28	8.127%	$67.3415	$67.34	$67.35	$67.30
Purchase #6	$10.28	11.462%	$11.4583	$11.46	$11.45	$11.50
Purchase #7	$119.91	9.862%	$131.7355	$131.74	$131.75	$131.70
7 purchase totals =	$889.19		$976.1711	$976.17	$976.15	$976.20