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	$38.40	6.800%	$41.0112	$41.01	$41.00	$41.00
Purchase #2	$18.29	3.113%	$18.8594	$18.86	$18.85	$18.90
Purchase #3	$12.91	8.560%	$14.0151	$14.02	$14.00	$14.00
Purchase #4	$250.69	10.838%	$277.8598	$277.86	$277.85	$277.90
Purchase #5	$36.31	7.123%	$38.8964	$38.90	$38.90	$38.90
Purchase #6	$133.96	12.255%	$150.3768	$150.38	$150.40	$150.40
Purchase #7	$23.26	4.296%	$24.2592	$24.26	$24.25	$24.30
7 purchase totals =	$513.82		$565.2779	$565.29	$565.25	$565.40