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	$83.77	5.453%	$88.338	$88.34	$88.35	$88.30
Purchase #2	$231.40	4.241%	$241.2137	$241.21	$241.20	$241.20
Purchase #3	$6.92	13.715%	$7.8691	$7.87	$7.85	$7.90
Purchase #4	$118.83	9.622%	$130.2638	$130.26	$130.25	$130.30
Purchase #5	$238.82	13.363%	$270.7335	$270.73	$270.75	$270.70
Purchase #6	$72.33	10.730%	$80.091	$80.09	$80.10	$80.10
Purchase #7	$242.98	5.317%	$255.8992	$255.90	$255.90	$255.90
7 purchase totals =	$995.05		$1,074.4083	$1,074.40	$1,074.40	$1,074.40