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	$111.28	11.529%	$124.1095	$124.11	$124.10	$124.10
Purchase #2	$102.75	3.113%	$105.9486	$105.95	$105.95	$105.90
Purchase #3	$200.99	10.678%	$222.4517	$222.45	$222.45	$222.50
Purchase #4	$90.68	5.757%	$95.9004	$95.90	$95.90	$95.90
Purchase #5	$148.38	7.284%	$159.188	$159.19	$159.20	$159.20
Purchase #6	$162.31	8.873%	$176.7118	$176.71	$176.70	$176.70
Purchase #7	$114.57	10.398%	$126.483	$126.48	$126.50	$126.50
7 purchase totals =	$930.96		$1,010.7930	$1,010.79	$1,010.80	$1,010.80