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	$34.73	8.285%	$37.6074	$37.61	$37.60	$37.60
Purchase #2	$169.28	12.631%	$190.6618	$190.66	$190.65	$190.70
Purchase #3	$85.40	11.536%	$95.2517	$95.25	$95.25	$95.30
Purchase #4	$68.66	3.427%	$71.013	$71.01	$71.00	$71.00
Purchase #5	$71.77	3.873%	$74.5497	$74.55	$74.55	$74.50
Purchase #6	$50.88	8.630%	$55.2709	$55.27	$55.25	$55.30
Purchase #7	$201.87	11.765%	$225.62	$225.62	$225.60	$225.60
7 purchase totals =	$682.59		$749.9745	$749.97	$749.90	$750.00