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	$51.95	12.827%	$58.6136	$58.61	$58.60	$58.60
Purchase #2	$56.54	7.380%	$60.7127	$60.71	$60.70	$60.70
Purchase #3	$150.94	10.229%	$166.3797	$166.38	$166.40	$166.40
Purchase #4	$128.76	10.780%	$142.6403	$142.64	$142.65	$142.60
Purchase #5	$63.91	3.105%	$65.8944	$65.89	$65.90	$65.90
Purchase #6	$91.61	5.350%	$96.5111	$96.51	$96.50	$96.50
Purchase #7	$229.33	11.567%	$255.8566	$255.86	$255.85	$255.90
7 purchase totals =	$773.04		$846.6084	$846.60	$846.60	$846.60