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	$135.55	9.380%	$148.2646	$148.26	$148.25	$148.30
Purchase #2	$35.48	6.334%	$37.7273	$37.73	$37.75	$37.70
Purchase #3	$40.58	12.356%	$45.5941	$45.59	$45.60	$45.60
Purchase #4	$238.50	9.780%	$261.8253	$261.83	$261.85	$261.80
Purchase #5	$168.57	7.847%	$181.7977	$181.80	$181.80	$181.80
Purchase #6	$116.70	13.552%	$132.5152	$132.52	$132.50	$132.50
Purchase #7	$162.44	13.605%	$184.54	$184.54	$184.55	$184.50
7 purchase totals =	$897.82		$992.2642	$992.27	$992.30	$992.20