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	$250.41	4.737%	$262.2719	$262.27	$262.25	$262.30
Purchase #2	$211.32	5.289%	$222.4967	$222.50	$222.50	$222.50
Purchase #3	$90.35	10.548%	$99.8801	$99.88	$99.90	$99.90
Purchase #4	$140.97	11.548%	$157.2492	$157.25	$157.25	$157.20
Purchase #5	$192.76	9.729%	$211.5136	$211.51	$211.50	$211.50
Purchase #6	$128.42	11.265%	$142.8865	$142.89	$142.90	$142.90
Purchase #7	$20.73	5.314%	$21.8316	$21.83	$21.85	$21.80
7 purchase totals =	$1,034.96		$1,118.1296	$1,118.13	$1,118.15	$1,118.10