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	$136.84	9.874%	$150.3516	$150.35	$150.35	$150.40
Purchase #2	$241.74	13.524%	$274.4329	$274.43	$274.45	$274.40
Purchase #3	$158.73	6.193%	$168.5601	$168.56	$168.55	$168.60
Purchase #4	$9.75	7.538%	$10.485	$10.49	$10.50	$10.50
Purchase #5	$40.76	3.787%	$42.3036	$42.30	$42.30	$42.30
Purchase #6	$147.95	4.805%	$155.059	$155.06	$155.05	$155.10
Purchase #7	$197.83	9.437%	$216.4992	$216.50	$216.50	$216.50
7 purchase totals =	$933.60		$1,017.6914	$1,017.69	$1,017.70	$1,017.80