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	$71.88	10.394%	$79.3512	$79.35	$79.35	$79.40
Purchase #2	$167.51	3.813%	$173.8972	$173.90	$173.90	$173.90
Purchase #3	$52.89	4.638%	$55.343	$55.34	$55.35	$55.30
Purchase #4	$177.85	10.492%	$196.51	$196.51	$196.50	$196.50
Purchase #5	$218.47	13.139%	$247.1748	$247.17	$247.15	$247.20
Purchase #6	$85.85	10.527%	$94.8874	$94.89	$94.90	$94.90
Purchase #7	$215.43	4.130%	$224.3273	$224.33	$224.35	$224.30
7 purchase totals =	$989.88		$1,071.4909	$1,071.49	$1,071.50	$1,071.50