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	$197.83	8.124%	$213.9017	$213.90	$213.90	$213.90
Purchase #2	$79.40	13.241%	$89.9134	$89.91	$89.90	$89.90
Purchase #3	$54.60	8.809%	$59.4097	$59.41	$59.40	$59.40
Purchase #4	$103.90	3.102%	$107.123	$107.12	$107.10	$107.10
Purchase #5	$90.34	11.863%	$101.057	$101.06	$101.05	$101.10
Purchase #6	$128.60	9.673%	$141.0395	$141.04	$141.05	$141.00
Purchase #7	$124.50	10.717%	$137.8427	$137.84	$137.85	$137.80
7 purchase totals =	$779.17		$850.2870	$850.28	$850.25	$850.20