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	$238.43	12.139%	$267.373	$267.37	$267.35	$267.40
Purchase #2	$150.43	6.173%	$159.716	$159.72	$159.70	$159.70
Purchase #3	$88.62	11.798%	$99.0754	$99.08	$99.10	$99.10
Purchase #4	$142.65	3.121%	$147.1021	$147.10	$147.10	$147.10
Purchase #5	$170.94	9.421%	$187.0443	$187.04	$187.05	$187.00
Purchase #6	$46.45	10.684%	$51.4127	$51.41	$51.40	$51.40
Purchase #7	$99.62	5.146%	$104.7464	$104.75	$104.75	$104.70
7 purchase totals =	$937.14		$1,016.4699	$1,016.47	$1,016.45	$1,016.40