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	$186.35	7.411%	$200.1604	$200.16	$200.15	$200.20
Purchase #2	$168.29	9.233%	$183.8282	$183.83	$183.85	$183.80
Purchase #3	$134.84	3.102%	$139.0227	$139.02	$139.00	$139.00
Purchase #4	$10.88	4.636%	$11.3844	$11.38	$11.40	$11.40
Purchase #5	$7.61	8.777%	$8.2779	$8.28	$8.30	$8.30
Purchase #6	$37.84	11.803%	$42.3063	$42.31	$42.30	$42.30
Purchase #7	$211.83	13.562%	$240.5584	$240.56	$240.55	$240.60
7 purchase totals =	$757.64		$825.5383	$825.54	$825.55	$825.60