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	$171.75	9.317%	$187.7519	$187.75	$187.75	$187.80
Purchase #2	$148.96	5.221%	$156.7372	$156.74	$156.75	$156.70
Purchase #3	$90.41	10.584%	$99.979	$99.98	$100.00	$100.00
Purchase #4	$156.75	13.664%	$178.1683	$178.17	$178.15	$178.20
Purchase #5	$145.77	7.335%	$156.4622	$156.46	$156.45	$156.50
Purchase #6	$50.78	13.676%	$57.7247	$57.72	$57.70	$57.70
Purchase #7	$186.74	12.659%	$210.3794	$210.38	$210.40	$210.40
7 purchase totals =	$951.16		$1,047.2027	$1,047.20	$1,047.20	$1,047.30