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	$170.90	9.367%	$186.9082	$186.91	$186.90	$186.90
Purchase #2	$219.39	12.535%	$246.8905	$246.89	$246.90	$246.90
Purchase #3	$191.46	4.595%	$200.2576	$200.26	$200.25	$200.30
Purchase #4	$224.46	4.585%	$234.7515	$234.75	$234.75	$234.80
Purchase #5	$147.74	12.667%	$166.4542	$166.45	$166.45	$166.50
Purchase #6	$80.32	8.501%	$87.148	$87.15	$87.15	$87.10
Purchase #7	$27.78	13.555%	$31.5456	$31.55	$31.55	$31.50
7 purchase totals =	$1,062.05		$1,153.9556	$1,153.96	$1,153.95	$1,154.00