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	$163.34	4.168%	$170.148	$170.15	$170.15	$170.10
Purchase #2	$238.67	11.507%	$266.1338	$266.13	$266.15	$266.10
Purchase #3	$179.79	10.531%	$198.7237	$198.72	$198.70	$198.70
Purchase #4	$63.88	13.351%	$72.4086	$72.41	$72.40	$72.40
Purchase #5	$177.92	10.668%	$196.9005	$196.90	$196.90	$196.90
Purchase #6	$186.72	5.352%	$196.7133	$196.71	$196.70	$196.70
Purchase #7	$65.52	11.484%	$73.0443	$73.04	$73.05	$73.00
7 purchase totals =	$1,075.84		$1,174.0722	$1,174.06	$1,174.05	$1,173.90