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	$160.69	4.614%	$168.1042	$168.10	$168.10	$168.10
Purchase #2	$108.71	7.532%	$116.898	$116.90	$116.90	$116.90
Purchase #3	$229.98	3.122%	$237.16	$237.16	$237.15	$237.20
Purchase #4	$191.41	9.133%	$208.8915	$208.89	$208.90	$208.90
Purchase #5	$245.72	6.424%	$261.5051	$261.51	$261.50	$261.50
Purchase #6	$70.96	10.631%	$78.5038	$78.50	$78.50	$78.50
Purchase #7	$215.33	8.222%	$233.0344	$233.03	$233.05	$233.00
7 purchase totals =	$1,222.80		$1,304.0970	$1,304.09	$1,304.10	$1,304.10