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	$216.43	6.553%	$230.6127	$230.61	$230.60	$230.60
Purchase #2	$212.65	6.467%	$226.4021	$226.40	$226.40	$226.40
Purchase #3	$5.92	10.695%	$6.5531	$6.55	$6.55	$6.60
Purchase #4	$197.53	12.607%	$222.4326	$222.43	$222.45	$222.40
Purchase #5	$55.82	6.660%	$59.5376	$59.54	$59.55	$59.50
Purchase #6	$28.36	11.314%	$31.5687	$31.57	$31.55	$31.60
Purchase #7	$207.35	9.177%	$226.3785	$226.38	$226.40	$226.40
7 purchase totals =	$924.06		$1,003.4853	$1,003.48	$1,003.50	$1,003.50