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	$183.51	9.188%	$200.3709	$200.37	$200.35	$200.40
Purchase #2	$98.71	6.333%	$104.9613	$104.96	$104.95	$105.00
Purchase #3	$242.40	10.710%	$268.361	$268.36	$268.35	$268.40
Purchase #4	$164.69	4.776%	$172.5556	$172.56	$172.55	$172.60
Purchase #5	$208.59	4.514%	$218.0058	$218.01	$218.00	$218.00
Purchase #6	$11.88	4.495%	$12.414	$12.41	$12.40	$12.40
Purchase #7	$84.83	8.687%	$92.1992	$92.20	$92.20	$92.20
7 purchase totals =	$994.61		$1,068.8678	$1,068.87	$1,068.80	$1,069.00