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	$73.34	8.277%	$79.4104	$79.41	$79.40	$79.40
Purchase #2	$161.89	12.859%	$182.7074	$182.71	$182.70	$182.70
Purchase #3	$121.99	4.461%	$127.432	$127.43	$127.45	$127.40
Purchase #4	$136.73	3.776%	$141.8929	$141.89	$141.90	$141.90
Purchase #5	$126.81	3.758%	$131.5755	$131.58	$131.60	$131.60
Purchase #6	$241.93	9.485%	$264.8771	$264.88	$264.90	$264.90
Purchase #7	$151.72	3.224%	$156.6115	$156.61	$156.60	$156.60
7 purchase totals =	$1,014.41		$1,084.5068	$1,084.51	$1,084.55	$1,084.50