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	$169.69	4.749%	$177.7486	$177.75	$177.75	$177.70
Purchase #2	$196.50	7.860%	$211.9449	$211.94	$211.95	$211.90
Purchase #3	$73.85	11.684%	$82.4786	$82.48	$82.50	$82.50
Purchase #4	$179.27	3.111%	$184.8471	$184.85	$184.85	$184.80
Purchase #5	$128.82	5.636%	$136.0803	$136.08	$136.10	$136.10
Purchase #6	$38.71	10.873%	$42.9189	$42.92	$42.90	$42.90
Purchase #7	$241.33	3.123%	$248.8667	$248.87	$248.85	$248.90
7 purchase totals =	$1,028.17		$1,084.8851	$1,084.89	$1,084.90	$1,084.80