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	$228.65	4.207%	$238.2693	$238.27	$238.25	$238.30
Purchase #2	$54.85	3.325%	$56.6738	$56.67	$56.65	$56.70
Purchase #3	$142.38	3.618%	$147.5313	$147.53	$147.55	$147.50
Purchase #4	$109.70	4.225%	$114.3348	$114.33	$114.35	$114.30
Purchase #5	$250.92	9.253%	$274.1376	$274.14	$274.15	$274.10
Purchase #6	$134.51	5.541%	$141.9632	$141.96	$141.95	$142.00
Purchase #7	$102.66	8.579%	$111.4672	$111.47	$111.45	$111.50
7 purchase totals =	$1,023.67		$1,084.3772	$1,084.37	$1,084.35	$1,084.40