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	$53.90	8.528%	$58.4966	$58.50	$58.50	$58.50
Purchase #2	$24.90	8.868%	$27.1081	$27.11	$27.10	$27.10
Purchase #3	$223.55	6.859%	$238.8833	$238.88	$238.90	$238.90
Purchase #4	$133.50	12.834%	$150.6334	$150.63	$150.65	$150.60
Purchase #5	$42.44	5.806%	$44.9041	$44.90	$44.90	$44.90
Purchase #6	$52.83	7.256%	$56.6633	$56.66	$56.65	$56.70
Purchase #7	$34.27	9.572%	$37.5503	$37.55	$37.55	$37.60
7 purchase totals =	$565.39		$614.2391	$614.23	$614.25	$614.30