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	$124.64	4.317%	$130.0207	$130.02	$130.00	$130.00
Purchase #2	$6.96	7.333%	$7.4704	$7.47	$7.45	$7.50
Purchase #3	$75.91	8.674%	$82.4944	$82.49	$82.50	$82.50
Purchase #4	$146.78	6.788%	$156.7434	$156.74	$156.75	$156.70
Purchase #5	$68.85	7.213%	$73.8162	$73.82	$73.80	$73.80
Purchase #6	$243.27	4.856%	$255.0832	$255.08	$255.10	$255.10
Purchase #7	$136.44	13.251%	$154.5197	$154.52	$154.50	$154.50
7 purchase totals =	$802.85		$860.1480	$860.14	$860.10	$860.10