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	$240.31	13.792%	$273.4536	$273.45	$273.45	$273.50
Purchase #2	$38.62	8.435%	$41.8776	$41.88	$41.90	$41.90
Purchase #3	$248.32	8.783%	$270.1299	$270.13	$270.15	$270.10
Purchase #4	$241.76	7.310%	$259.4327	$259.43	$259.45	$259.40
Purchase #5	$95.45	10.326%	$105.3062	$105.31	$105.30	$105.30
Purchase #6	$83.56	10.377%	$92.231	$92.23	$92.25	$92.20
Purchase #7	$167.85	8.229%	$181.6624	$181.66	$181.65	$181.70
7 purchase totals =	$1,115.87		$1,224.0934	$1,224.09	$1,224.15	$1,224.10