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	$190.71	3.117%	$196.6544	$196.65	$196.65	$196.70
Purchase #2	$53.87	10.422%	$59.4843	$59.48	$59.50	$59.50
Purchase #3	$20.66	13.573%	$23.4642	$23.46	$23.45	$23.50
Purchase #4	$152.90	12.152%	$171.4804	$171.48	$171.50	$171.50
Purchase #5	$231.37	4.701%	$242.2467	$242.25	$242.25	$242.20
Purchase #6	$130.76	4.368%	$136.4716	$136.47	$136.45	$136.50
Purchase #7	$24.60	10.563%	$27.1985	$27.20	$27.20	$27.20
7 purchase totals =	$804.87		$857.0001	$856.99	$857.00	$857.10