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	$198.59	7.303%	$213.093	$213.09	$213.10	$213.10
Purchase #2	$130.82	9.830%	$143.6796	$143.68	$143.70	$143.70
Purchase #3	$165.31	13.370%	$187.4119	$187.41	$187.40	$187.40
Purchase #4	$92.34	13.672%	$104.9647	$104.96	$104.95	$105.00
Purchase #5	$212.89	4.460%	$222.3849	$222.38	$222.40	$222.40
Purchase #6	$208.88	4.607%	$218.5031	$218.50	$218.50	$218.50
Purchase #7	$128.46	12.416%	$144.4096	$144.41	$144.40	$144.40
7 purchase totals =	$1,137.29		$1,234.4468	$1,234.43	$1,234.45	$1,234.50