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	$248.50	9.598%	$272.351	$272.35	$272.35	$272.40
Purchase #2	$163.90	9.654%	$179.7229	$179.72	$179.70	$179.70
Purchase #3	$200.94	11.282%	$223.6101	$223.61	$223.60	$223.60
Purchase #4	$92.76	6.814%	$99.0807	$99.08	$99.10	$99.10
Purchase #5	$30.52	6.255%	$32.429	$32.43	$32.45	$32.40
Purchase #6	$154.66	3.776%	$160.5	$160.50	$160.50	$160.50
Purchase #7	$156.49	13.695%	$177.9213	$177.92	$177.90	$177.90
7 purchase totals =	$1,047.77		$1,145.6150	$1,145.61	$1,145.60	$1,145.60