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	$153.38	3.613%	$158.9216	$158.92	$158.90	$158.90
Purchase #2	$69.90	3.485%	$72.336	$72.34	$72.35	$72.30
Purchase #3	$9.68	12.497%	$10.8897	$10.89	$10.90	$10.90
Purchase #4	$212.33	8.601%	$230.5925	$230.59	$230.60	$230.60
Purchase #5	$206.41	3.342%	$213.3082	$213.31	$213.30	$213.30
Purchase #6	$206.89	7.729%	$222.8805	$222.88	$222.90	$222.90
Purchase #7	$223.77	4.807%	$234.5266	$234.53	$234.55	$234.50
7 purchase totals =	$1,082.36		$1,143.4551	$1,143.46	$1,143.50	$1,143.40