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	$177.70	10.475%	$196.3141	$196.31	$196.30	$196.30
Purchase #2	$104.90	6.469%	$111.686	$111.69	$111.70	$111.70
Purchase #3	$94.51	11.253%	$105.1452	$105.15	$105.15	$105.10
Purchase #4	$207.98	7.852%	$224.3106	$224.31	$224.30	$224.30
Purchase #5	$243.72	4.176%	$253.8977	$253.90	$253.90	$253.90
Purchase #6	$41.73	6.701%	$44.5263	$44.53	$44.55	$44.50
Purchase #7	$168.73	5.266%	$177.6153	$177.62	$177.60	$177.60
7 purchase totals =	$1,039.27		$1,113.4952	$1,113.51	$1,113.50	$1,113.40