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	$39.76	13.779%	$45.2385	$45.24	$45.25	$45.20
Purchase #2	$118.54	7.332%	$127.2314	$127.23	$127.25	$127.20
Purchase #3	$126.89	4.565%	$132.6825	$132.68	$132.70	$132.70
Purchase #4	$171.28	6.713%	$182.778	$182.78	$182.80	$182.80
Purchase #5	$208.25	9.236%	$227.484	$227.48	$227.50	$227.50
Purchase #6	$228.66	9.173%	$249.635	$249.64	$249.65	$249.60
Purchase #7	$79.93	9.495%	$87.5194	$87.52	$87.50	$87.50
7 purchase totals =	$973.31		$1,052.5688	$1,052.57	$1,052.65	$1,052.50