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	$187.49	4.690%	$196.2833	$196.28	$196.30	$196.30
Purchase #2	$234.86	9.827%	$257.9397	$257.94	$257.95	$257.90
Purchase #3	$35.94	5.472%	$37.9066	$37.91	$37.90	$37.90
Purchase #4	$197.54	13.855%	$224.9092	$224.91	$224.90	$224.90
Purchase #5	$104.62	7.449%	$112.4131	$112.41	$112.40	$112.40
Purchase #6	$65.89	8.256%	$71.3299	$71.33	$71.35	$71.30
Purchase #7	$223.76	8.500%	$242.7796	$242.78	$242.80	$242.80
7 purchase totals =	$1,050.10		$1,143.5614	$1,143.56	$1,143.60	$1,143.50