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	$148.40	9.118%	$161.9311	$161.93	$161.95	$161.90
Purchase #2	$227.28	10.327%	$250.7512	$250.75	$250.75	$250.80
Purchase #3	$71.92	9.675%	$78.8783	$78.88	$78.90	$78.90
Purchase #4	$115.55	4.537%	$120.7925	$120.79	$120.80	$120.80
Purchase #5	$102.93	5.421%	$108.5098	$108.51	$108.50	$108.50
Purchase #6	$56.27	5.401%	$59.3091	$59.31	$59.30	$59.30
Purchase #7	$140.73	9.455%	$154.036	$154.04	$154.05	$154.00
7 purchase totals =	$863.08		$934.2080	$934.21	$934.25	$934.20