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	$141.88	6.416%	$150.983	$150.98	$151.00	$151.00
Purchase #2	$36.59	3.193%	$37.7583	$37.76	$37.75	$37.80
Purchase #3	$100.95	4.481%	$105.4736	$105.47	$105.45	$105.50
Purchase #4	$21.40	4.746%	$22.4156	$22.42	$22.40	$22.40
Purchase #5	$201.86	12.549%	$227.1914	$227.19	$227.20	$227.20
Purchase #6	$182.73	13.576%	$207.5374	$207.54	$207.55	$207.50
Purchase #7	$199.90	11.835%	$223.5582	$223.56	$223.55	$223.60
7 purchase totals =	$885.31		$974.9175	$974.92	$974.90	$975.00