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	$234.80	4.296%	$244.887	$244.89	$244.90	$244.90
Purchase #2	$162.28	7.372%	$174.2433	$174.24	$174.25	$174.20
Purchase #3	$7.59	9.683%	$8.3249	$8.32	$8.30	$8.30
Purchase #4	$62.29	7.349%	$66.8677	$66.87	$66.85	$66.90
Purchase #5	$71.37	10.566%	$78.911	$78.91	$78.90	$78.90
Purchase #6	$59.91	11.353%	$66.7116	$66.71	$66.70	$66.70
Purchase #7	$70.96	10.601%	$78.4825	$78.48	$78.50	$78.50
7 purchase totals =	$669.20		$718.4280	$718.42	$718.40	$718.40