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	$222.67	13.354%	$252.4054	$252.41	$252.40	$252.40
Purchase #2	$165.67	6.174%	$175.8985	$175.90	$175.90	$175.90
Purchase #3	$190.71	13.335%	$216.1412	$216.14	$216.15	$216.10
Purchase #4	$55.33	6.836%	$59.1124	$59.11	$59.10	$59.10
Purchase #5	$26.89	7.725%	$28.9673	$28.97	$28.95	$29.00
Purchase #6	$60.60	5.710%	$64.0603	$64.06	$64.05	$64.10
Purchase #7	$70.52	11.473%	$78.6108	$78.61	$78.60	$78.60
7 purchase totals =	$792.39		$875.1959	$875.20	$875.15	$875.20