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	$249.64	10.102%	$274.8586	$274.86	$274.85	$274.90
Purchase #2	$125.64	4.639%	$131.4684	$131.47	$131.45	$131.50
Purchase #3	$100.90	4.685%	$105.6272	$105.63	$105.65	$105.60
Purchase #4	$214.41	6.532%	$228.4153	$228.42	$228.40	$228.40
Purchase #5	$214.93	3.822%	$223.1446	$223.14	$223.15	$223.10
Purchase #6	$109.62	8.108%	$118.508	$118.51	$118.50	$118.50
Purchase #7	$23.27	11.343%	$25.9095	$25.91	$25.90	$25.90
7 purchase totals =	$1,038.41		$1,107.9316	$1,107.94	$1,107.90	$1,107.90