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	$203.44	11.643%	$227.1265	$227.13	$227.15	$227.10
Purchase #2	$189.67	3.721%	$196.7276	$196.73	$196.75	$196.70
Purchase #3	$118.80	8.326%	$128.6913	$128.69	$128.70	$128.70
Purchase #4	$35.57	5.203%	$37.4207	$37.42	$37.40	$37.40
Purchase #5	$52.90	11.649%	$59.0623	$59.06	$59.05	$59.10
Purchase #6	$71.26	3.759%	$73.9387	$73.94	$73.95	$73.90
Purchase #7	$34.33	10.868%	$38.061	$38.06	$38.05	$38.10
7 purchase totals =	$705.97		$761.0281	$761.03	$761.05	$761.00