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	$140.38	11.802%	$156.9476	$156.95	$156.95	$156.90
Purchase #2	$69.44	12.657%	$78.229	$78.23	$78.25	$78.20
Purchase #3	$33.42	13.656%	$37.9838	$37.98	$38.00	$38.00
Purchase #4	$92.45	3.651%	$95.8253	$95.83	$95.85	$95.80
Purchase #5	$73.43	9.459%	$80.3757	$80.38	$80.40	$80.40
Purchase #6	$135.32	6.379%	$143.9521	$143.95	$143.95	$144.00
Purchase #7	$189.72	6.588%	$202.2188	$202.22	$202.20	$202.20
7 purchase totals =	$734.16		$795.5323	$795.54	$795.60	$795.50