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	$200.59	7.747%	$216.1297	$216.13	$216.15	$216.10
Purchase #2	$217.68	6.506%	$231.8423	$231.84	$231.85	$231.80
Purchase #3	$95.33	9.593%	$104.475	$104.48	$104.50	$104.50
Purchase #4	$70.56	11.408%	$78.6095	$78.61	$78.60	$78.60
Purchase #5	$43.91	7.767%	$47.3205	$47.32	$47.30	$47.30
Purchase #6	$207.37	12.746%	$233.8014	$233.80	$233.80	$233.80
Purchase #7	$194.26	5.472%	$204.8899	$204.89	$204.90	$204.90
7 purchase totals =	$1,029.70		$1,117.0683	$1,117.07	$1,117.10	$1,117.00