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	$171.69	12.415%	$193.0053	$193.01	$193.00	$193.00
Purchase #2	$133.81	5.693%	$141.4278	$141.43	$141.45	$141.40
Purchase #3	$120.45	6.649%	$128.4587	$128.46	$128.45	$128.50
Purchase #4	$92.26	6.376%	$98.1425	$98.14	$98.15	$98.10
Purchase #5	$40.44	7.573%	$43.5025	$43.50	$43.50	$43.50
Purchase #6	$153.53	12.654%	$172.9577	$172.96	$172.95	$173.00
Purchase #7	$183.78	6.717%	$196.1245	$196.12	$196.10	$196.10
7 purchase totals =	$895.96		$973.6190	$973.62	$973.60	$973.60