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	$207.59	8.203%	$224.6186	$224.62	$224.60	$224.60
Purchase #2	$61.27	12.850%	$69.1432	$69.14	$69.15	$69.10
Purchase #3	$62.78	13.697%	$71.379	$71.38	$71.40	$71.40
Purchase #4	$98.58	6.391%	$104.8802	$104.88	$104.90	$104.90
Purchase #5	$181.45	8.249%	$196.4178	$196.42	$196.40	$196.40
Purchase #6	$54.73	8.370%	$59.3109	$59.31	$59.30	$59.30
Purchase #7	$188.31	12.841%	$212.4909	$212.49	$212.50	$212.50
7 purchase totals =	$854.71		$938.2406	$938.24	$938.25	$938.20