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	$105.46	5.263%	$111.0104	$111.01	$111.00	$111.00
Purchase #2	$83.53	13.238%	$94.5877	$94.59	$94.60	$94.60
Purchase #3	$167.43	10.306%	$184.6853	$184.69	$184.70	$184.70
Purchase #4	$65.87	9.688%	$72.2515	$72.25	$72.25	$72.30
Purchase #5	$221.95	4.802%	$232.608	$232.61	$232.60	$232.60
Purchase #6	$54.71	6.321%	$58.1682	$58.17	$58.15	$58.20
Purchase #7	$146.89	6.429%	$156.3336	$156.33	$156.35	$156.30
7 purchase totals =	$845.84		$909.6447	$909.65	$909.65	$909.70