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	$132.57	3.224%	$136.8441	$136.84	$136.85	$136.80
Purchase #2	$80.68	11.149%	$89.675	$89.68	$89.70	$89.70
Purchase #3	$175.67	6.342%	$186.811	$186.81	$186.80	$186.80
Purchase #4	$165.42	13.854%	$188.3373	$188.34	$188.35	$188.30
Purchase #5	$101.56	3.860%	$105.4802	$105.48	$105.50	$105.50
Purchase #6	$105.88	6.168%	$112.4107	$112.41	$112.40	$112.40
Purchase #7	$85.59	7.828%	$92.29	$92.29	$92.30	$92.30
7 purchase totals =	$847.37		$911.8483	$911.85	$911.90	$911.80