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	$61.59	12.714%	$69.4206	$69.42	$69.40	$69.40
Purchase #2	$170.68	3.539%	$176.7204	$176.72	$176.70	$176.70
Purchase #3	$176.42	11.553%	$196.8018	$196.80	$196.80	$196.80
Purchase #4	$161.60	8.258%	$174.9449	$174.94	$174.95	$174.90
Purchase #5	$173.34	7.671%	$186.6369	$186.64	$186.65	$186.60
Purchase #6	$98.40	3.209%	$101.5577	$101.56	$101.55	$101.60
Purchase #7	$169.65	6.374%	$180.4635	$180.46	$180.45	$180.50
7 purchase totals =	$1,011.68		$1,086.5458	$1,086.54	$1,086.50	$1,086.50