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	$169.52	11.461%	$188.9487	$188.95	$188.95	$188.90
Purchase #2	$179.60	7.190%	$192.5132	$192.51	$192.50	$192.50
Purchase #3	$103.86	4.285%	$108.3104	$108.31	$108.30	$108.30
Purchase #4	$182.36	3.492%	$188.728	$188.73	$188.75	$188.70
Purchase #5	$58.97	8.338%	$63.8869	$63.89	$63.90	$63.90
Purchase #6	$52.85	12.671%	$59.5466	$59.55	$59.55	$59.50
Purchase #7	$43.39	9.724%	$47.6092	$47.61	$47.60	$47.60
7 purchase totals =	$790.55		$849.5430	$849.55	$849.55	$849.40