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	$154.38	3.276%	$159.4375	$159.44	$159.45	$159.40
Purchase #2	$6.76	8.302%	$7.3212	$7.32	$7.30	$7.30
Purchase #3	$169.55	7.328%	$181.9746	$181.97	$181.95	$182.00
Purchase #4	$116.72	6.115%	$123.8574	$123.86	$123.85	$123.90
Purchase #5	$48.36	9.230%	$52.8236	$52.82	$52.80	$52.80
Purchase #6	$229.25	3.111%	$236.382	$236.38	$236.40	$236.40
Purchase #7	$133.32	13.597%	$151.4475	$151.45	$151.45	$151.40
7 purchase totals =	$858.34		$913.2438	$913.24	$913.20	$913.20