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	$196.92	6.313%	$209.3516	$209.35	$209.35	$209.40
Purchase #2	$224.46	10.758%	$248.6074	$248.61	$248.60	$248.60
Purchase #3	$69.71	3.867%	$72.4057	$72.41	$72.40	$72.40
Purchase #4	$99.87	13.116%	$112.9689	$112.97	$112.95	$113.00
Purchase #5	$104.88	3.820%	$108.8864	$108.89	$108.90	$108.90
Purchase #6	$228.60	12.155%	$256.3863	$256.39	$256.40	$256.40
Purchase #7	$223.64	9.778%	$245.5075	$245.51	$245.50	$245.50
7 purchase totals =	$1,148.08		$1,254.1138	$1,254.13	$1,254.10	$1,254.20