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	$165.78	3.115%	$170.944	$170.94	$170.95	$170.90
Purchase #2	$98.80	11.554%	$110.2154	$110.22	$110.20	$110.20
Purchase #3	$86.79	3.856%	$90.1366	$90.14	$90.15	$90.10
Purchase #4	$225.85	13.145%	$255.538	$255.54	$255.55	$255.50
Purchase #5	$43.61	3.465%	$45.1211	$45.12	$45.10	$45.10
Purchase #6	$11.51	11.169%	$12.7956	$12.80	$12.80	$12.80
Purchase #7	$81.32	13.596%	$92.3763	$92.38	$92.40	$92.40
7 purchase totals =	$713.66		$777.1270	$777.14	$777.15	$777.00