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	$113.41	12.644%	$127.7496	$127.75	$127.75	$127.70
Purchase #2	$172.97	5.177%	$181.9247	$181.92	$181.90	$181.90
Purchase #3	$39.54	6.836%	$42.243	$42.24	$42.25	$42.20
Purchase #4	$241.74	8.315%	$261.8407	$261.84	$261.85	$261.80
Purchase #5	$245.94	6.827%	$262.7303	$262.73	$262.75	$262.70
Purchase #6	$211.86	13.537%	$240.5395	$240.54	$240.55	$240.50
Purchase #7	$43.40	11.591%	$48.4305	$48.43	$48.45	$48.40
7 purchase totals =	$1,068.86		$1,165.4583	$1,165.45	$1,165.50	$1,165.20