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	$126.50	12.422%	$142.2138	$142.21	$142.20	$142.20
Purchase #2	$78.55	6.180%	$83.4044	$83.40	$83.40	$83.40
Purchase #3	$201.81	8.638%	$219.2423	$219.24	$219.25	$219.20
Purchase #4	$57.81	10.606%	$63.9413	$63.94	$63.95	$63.90
Purchase #5	$229.36	11.554%	$255.8603	$255.86	$255.85	$255.90
Purchase #6	$77.46	6.396%	$82.4143	$82.41	$82.40	$82.40
Purchase #7	$72.26	9.280%	$78.9657	$78.97	$78.95	$79.00
7 purchase totals =	$843.75		$926.0421	$926.03	$926.00	$926.00