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	$89.62	6.387%	$95.344	$95.34	$95.35	$95.30
Purchase #2	$80.37	6.166%	$85.3256	$85.33	$85.35	$85.30
Purchase #3	$239.75	10.622%	$265.2162	$265.22	$265.20	$265.20
Purchase #4	$113.60	5.192%	$119.4981	$119.50	$119.50	$119.50
Purchase #5	$91.44	8.604%	$99.3075	$99.31	$99.30	$99.30
Purchase #6	$201.27	7.226%	$215.8138	$215.81	$215.80	$215.80
Purchase #7	$103.25	10.650%	$114.2461	$114.25	$114.25	$114.20
7 purchase totals =	$919.30		$994.7513	$994.76	$994.75	$994.60