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	$156.96	12.600%	$176.737	$176.74	$176.75	$176.70
Purchase #2	$143.81	3.414%	$148.7197	$148.72	$148.70	$148.70
Purchase #3	$203.44	9.528%	$222.8238	$222.82	$222.80	$222.80
Purchase #4	$24.41	3.342%	$25.2258	$25.23	$25.25	$25.20
Purchase #5	$70.89	11.351%	$78.9367	$78.94	$78.95	$78.90
Purchase #6	$191.90	5.643%	$202.7289	$202.73	$202.75	$202.70
Purchase #7	$179.45	4.356%	$187.2668	$187.27	$187.25	$187.30
7 purchase totals =	$970.86		$1,042.4387	$1,042.45	$1,042.45	$1,042.30