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	$241.47	7.161%	$258.7617	$258.76	$258.75	$258.80
Purchase #2	$103.75	9.288%	$113.3863	$113.39	$113.40	$113.40
Purchase #3	$64.67	4.673%	$67.692	$67.69	$67.70	$67.70
Purchase #4	$26.87	6.576%	$28.637	$28.64	$28.65	$28.60
Purchase #5	$234.93	6.800%	$250.9052	$250.91	$250.90	$250.90
Purchase #6	$165.88	11.459%	$184.8882	$184.89	$184.90	$184.90
Purchase #7	$150.86	9.292%	$164.8779	$164.88	$164.90	$164.90
7 purchase totals =	$988.43		$1,069.1483	$1,069.16	$1,069.20	$1,069.20