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	$162.87	7.337%	$174.8198	$174.82	$174.80	$174.80
Purchase #2	$151.71	9.394%	$165.9616	$165.96	$165.95	$166.00
Purchase #3	$206.36	7.641%	$222.128	$222.13	$222.15	$222.10
Purchase #4	$159.70	5.402%	$168.327	$168.33	$168.35	$168.30
Purchase #5	$88.61	7.517%	$95.2708	$95.27	$95.25	$95.30
Purchase #6	$178.65	13.691%	$203.109	$203.11	$203.10	$203.10
Purchase #7	$49.33	11.103%	$54.8071	$54.81	$54.80	$54.80
7 purchase totals =	$997.23		$1,084.4233	$1,084.43	$1,084.40	$1,084.40