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	$76.27	13.325%	$86.433	$86.43	$86.45	$86.40
Purchase #2	$50.75	5.835%	$53.7113	$53.71	$53.70	$53.70
Purchase #3	$31.61	13.516%	$35.8824	$35.88	$35.90	$35.90
Purchase #4	$24.78	12.826%	$27.9583	$27.96	$27.95	$28.00
Purchase #5	$70.42	12.744%	$79.3943	$79.39	$79.40	$79.40
Purchase #6	$39.68	9.739%	$43.5444	$43.54	$43.55	$43.50
Purchase #7	$94.47	6.678%	$100.7787	$100.78	$100.80	$100.80
7 purchase totals =	$387.98		$427.7024	$427.69	$427.75	$427.70