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	$61.88	5.656%	$65.3799	$65.38	$65.40	$65.40
Purchase #2	$95.78	3.841%	$99.4589	$99.46	$99.45	$99.50
Purchase #3	$155.71	8.789%	$169.3954	$169.40	$169.40	$169.40
Purchase #4	$50.84	12.466%	$57.1777	$57.18	$57.20	$57.20
Purchase #5	$202.66	6.527%	$215.8876	$215.89	$215.90	$215.90
Purchase #6	$64.43	12.163%	$72.2666	$72.27	$72.25	$72.30
Purchase #7	$91.89	11.854%	$102.7826	$102.78	$102.80	$102.80
7 purchase totals =	$723.19		$782.3487	$782.36	$782.40	$782.50