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	$167.52	6.330%	$178.124	$178.12	$178.10	$178.10
Purchase #2	$30.47	5.154%	$32.0404	$32.04	$32.05	$32.00
Purchase #3	$222.54	6.860%	$237.8062	$237.81	$237.80	$237.80
Purchase #4	$233.51	12.403%	$262.4722	$262.47	$262.45	$262.50
Purchase #5	$171.84	9.413%	$188.0153	$188.02	$188.00	$188.00
Purchase #6	$38.27	10.183%	$42.167	$42.17	$42.15	$42.20
Purchase #7	$154.60	7.124%	$165.6137	$165.61	$165.60	$165.60
7 purchase totals =	$1,018.75		$1,106.2388	$1,106.24	$1,106.15	$1,106.20