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	$135.31	5.837%	$143.208	$143.21	$143.20	$143.20
Purchase #2	$95.49	5.593%	$100.8308	$100.83	$100.85	$100.80
Purchase #3	$88.70	13.376%	$100.5645	$100.56	$100.55	$100.60
Purchase #4	$239.38	10.537%	$264.6035	$264.60	$264.60	$264.60
Purchase #5	$57.86	6.562%	$61.6568	$61.66	$61.65	$61.70
Purchase #6	$210.33	7.172%	$225.4149	$225.41	$225.40	$225.40
Purchase #7	$186.98	3.459%	$193.4476	$193.45	$193.45	$193.40
7 purchase totals =	$1,014.05		$1,089.7261	$1,089.72	$1,089.70	$1,089.70