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	$201.91	4.670%	$211.3392	$211.34	$211.35	$211.30
Purchase #2	$102.69	12.457%	$115.4821	$115.48	$115.50	$115.50
Purchase #3	$128.44	11.251%	$142.8908	$142.89	$142.90	$142.90
Purchase #4	$177.72	7.192%	$190.5016	$190.50	$190.50	$190.50
Purchase #5	$24.55	11.205%	$27.3008	$27.30	$27.30	$27.30
Purchase #6	$89.51	12.250%	$100.475	$100.48	$100.50	$100.50
Purchase #7	$87.58	9.246%	$95.6776	$95.68	$95.70	$95.70
7 purchase totals =	$812.40		$883.6671	$883.67	$883.75	$883.70