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	$116.70	11.528%	$130.1532	$130.15	$130.15	$130.20
Purchase #2	$227.66	7.392%	$244.4886	$244.49	$244.50	$244.50
Purchase #3	$250.38	13.158%	$283.325	$283.33	$283.35	$283.30
Purchase #4	$114.31	12.171%	$128.2227	$128.22	$128.20	$128.20
Purchase #5	$65.88	10.621%	$72.8771	$72.88	$72.90	$72.90
Purchase #6	$237.62	10.608%	$262.8267	$262.83	$262.85	$262.80
Purchase #7	$55.61	11.107%	$61.7866	$61.79	$61.80	$61.80
7 purchase totals =	$1,068.16		$1,183.6799	$1,183.69	$1,183.75	$1,183.70