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	$68.94	13.352%	$78.1449	$78.14	$78.15	$78.10
Purchase #2	$248.53	3.687%	$257.6933	$257.69	$257.70	$257.70
Purchase #3	$247.71	4.339%	$258.4581	$258.46	$258.45	$258.50
Purchase #4	$65.32	6.266%	$69.413	$69.41	$69.40	$69.40
Purchase #5	$248.29	12.174%	$278.5168	$278.52	$278.50	$278.50
Purchase #6	$45.48	10.808%	$50.3955	$50.40	$50.40	$50.40
Purchase #7	$80.87	6.241%	$85.9171	$85.92	$85.90	$85.90
7 purchase totals =	$1,005.14		$1,078.5387	$1,078.54	$1,078.50	$1,078.50