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	$139.34	4.232%	$145.2369	$145.24	$145.25	$145.20
Purchase #2	$69.60	5.767%	$73.6138	$73.61	$73.60	$73.60
Purchase #3	$188.71	6.151%	$200.3176	$200.32	$200.30	$200.30
Purchase #4	$246.38	3.819%	$255.7893	$255.79	$255.80	$255.80
Purchase #5	$39.72	4.679%	$41.5785	$41.58	$41.60	$41.60
Purchase #6	$187.89	8.264%	$203.4172	$203.42	$203.40	$203.40
Purchase #7	$160.29	4.843%	$168.0528	$168.05	$168.05	$168.10
7 purchase totals =	$1,031.93		$1,088.0061	$1,088.01	$1,088.00	$1,088.00