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	$160.85	13.463%	$182.5052	$182.51	$182.50	$182.50
Purchase #2	$245.60	3.563%	$254.3507	$254.35	$254.35	$254.40
Purchase #3	$65.54	10.679%	$72.539	$72.54	$72.55	$72.50
Purchase #4	$140.33	11.596%	$156.6027	$156.60	$156.60	$156.60
Purchase #5	$179.99	12.275%	$202.0838	$202.08	$202.10	$202.10
Purchase #6	$92.76	7.171%	$99.4118	$99.41	$99.40	$99.40
Purchase #7	$90.93	8.184%	$98.3717	$98.37	$98.35	$98.40
7 purchase totals =	$976.00		$1,065.8649	$1,065.86	$1,065.85	$1,065.90