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	$189.35	13.527%	$214.9634	$214.96	$214.95	$215.00
Purchase #2	$137.70	8.654%	$149.6166	$149.62	$149.60	$149.60
Purchase #3	$45.58	11.710%	$50.9174	$50.92	$50.90	$50.90
Purchase #4	$240.35	7.271%	$257.8258	$257.83	$257.85	$257.80
Purchase #5	$89.62	12.628%	$100.9372	$100.94	$100.95	$100.90
Purchase #6	$88.92	12.122%	$99.6989	$99.70	$99.70	$99.70
Purchase #7	$127.44	12.494%	$143.3624	$143.36	$143.35	$143.40
7 purchase totals =	$918.96		$1,017.3217	$1,017.33	$1,017.30	$1,017.30