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	$64.74	5.540%	$68.3266	$68.33	$68.35	$68.30
Purchase #2	$154.72	13.826%	$176.1116	$176.11	$176.10	$176.10
Purchase #3	$132.96	11.566%	$148.3382	$148.34	$148.35	$148.30
Purchase #4	$125.50	11.278%	$139.6539	$139.65	$139.65	$139.70
Purchase #5	$186.77	11.693%	$208.609	$208.61	$208.60	$208.60
Purchase #6	$52.56	12.753%	$59.263	$59.26	$59.25	$59.30
Purchase #7	$203.65	6.465%	$216.816	$216.82	$216.80	$216.80
7 purchase totals =	$920.90		$1,017.1183	$1,017.12	$1,017.10	$1,017.10