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	$67.52	4.544%	$70.5881	$70.59	$70.60	$70.60
Purchase #2	$211.64	3.671%	$219.4093	$219.41	$219.40	$219.40
Purchase #3	$33.89	10.768%	$37.5393	$37.54	$37.55	$37.50
Purchase #4	$18.90	3.483%	$19.5583	$19.56	$19.55	$19.60
Purchase #5	$198.82	10.643%	$219.9804	$219.98	$220.00	$220.00
Purchase #6	$172.31	13.857%	$196.187	$196.19	$196.20	$196.20
Purchase #7	$201.86	10.287%	$222.6253	$222.63	$222.65	$222.60
7 purchase totals =	$904.94		$985.8877	$985.90	$985.95	$985.90