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	$77.27	6.655%	$82.4123	$82.41	$82.40	$82.40
Purchase #2	$49.28	5.666%	$52.0722	$52.07	$52.05	$52.10
Purchase #3	$237.54	9.729%	$260.6503	$260.65	$260.65	$260.70
Purchase #4	$127.72	12.377%	$143.5279	$143.53	$143.55	$143.50
Purchase #5	$240.52	6.208%	$255.4515	$255.45	$255.45	$255.50
Purchase #6	$208.65	6.640%	$222.5044	$222.50	$222.50	$222.50
Purchase #7	$85.50	11.230%	$95.1017	$95.10	$95.10	$95.10
7 purchase totals =	$1,026.48		$1,111.7203	$1,111.71	$1,111.70	$1,111.80