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	$80.53	9.828%	$88.4445	$88.44	$88.45	$88.40
Purchase #2	$171.83	9.118%	$187.4975	$187.50	$187.50	$187.50
Purchase #3	$59.88	8.852%	$65.1806	$65.18	$65.20	$65.20
Purchase #4	$76.97	7.632%	$82.8444	$82.84	$82.85	$82.80
Purchase #5	$232.37	12.126%	$260.5472	$260.55	$260.55	$260.50
Purchase #6	$59.46	8.452%	$64.4856	$64.49	$64.50	$64.50
Purchase #7	$169.82	11.773%	$189.8129	$189.81	$189.80	$189.80
7 purchase totals =	$850.86		$938.8127	$938.81	$938.85	$938.70