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	$167.34	6.772%	$178.6723	$178.67	$178.65	$178.70
Purchase #2	$223.90	13.645%	$254.4512	$254.45	$254.45	$254.50
Purchase #3	$17.66	3.259%	$18.2355	$18.24	$18.25	$18.20
Purchase #4	$99.32	12.172%	$111.4092	$111.41	$111.40	$111.40
Purchase #5	$205.63	9.437%	$225.0353	$225.04	$225.05	$225.00
Purchase #6	$169.61	8.739%	$184.4322	$184.43	$184.45	$184.40
Purchase #7	$28.64	11.118%	$31.8242	$31.82	$31.80	$31.80
7 purchase totals =	$912.10		$1,004.0599	$1,004.06	$1,004.05	$1,004.00