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	$80.83	5.516%	$85.2886	$85.29	$85.30	$85.30
Purchase #2	$102.36	5.782%	$108.2785	$108.28	$108.30	$108.30
Purchase #3	$38.67	12.148%	$43.3676	$43.37	$43.35	$43.40
Purchase #4	$147.44	9.238%	$161.0605	$161.06	$161.05	$161.10
Purchase #5	$176.95	13.505%	$200.8471	$200.85	$200.85	$200.80
Purchase #6	$148.85	7.327%	$159.7562	$159.76	$159.75	$159.80
Purchase #7	$63.42	6.526%	$67.5588	$67.56	$67.55	$67.60
7 purchase totals =	$758.52		$826.1573	$826.17	$826.15	$826.30