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	$183.58	6.811%	$196.0836	$196.08	$196.10	$196.10
Purchase #2	$154.78	6.147%	$164.2943	$164.29	$164.30	$164.30
Purchase #3	$206.88	12.435%	$232.6055	$232.61	$232.60	$232.60
Purchase #4	$205.83	8.358%	$223.0333	$223.03	$223.05	$223.00
Purchase #5	$47.36	11.583%	$52.8457	$52.85	$52.85	$52.80
Purchase #6	$30.79	13.297%	$34.8841	$34.88	$34.90	$34.90
Purchase #7	$105.42	3.448%	$109.0549	$109.05	$109.05	$109.10
7 purchase totals =	$934.64		$1,012.8014	$1,012.79	$1,012.85	$1,012.80