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	$201.64	7.497%	$216.757	$216.76	$216.75	$216.80
Purchase #2	$107.42	3.768%	$111.4676	$111.47	$111.45	$111.50
Purchase #3	$227.40	4.794%	$238.3016	$238.30	$238.30	$238.30
Purchase #4	$220.89	6.120%	$234.4085	$234.41	$234.40	$234.40
Purchase #5	$140.33	8.596%	$152.3928	$152.39	$152.40	$152.40
Purchase #6	$32.89	3.264%	$33.9635	$33.96	$33.95	$34.00
Purchase #7	$250.99	11.518%	$279.899	$279.90	$279.90	$279.90
7 purchase totals =	$1,181.56		$1,267.1900	$1,267.19	$1,267.15	$1,267.30