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	$31.75	13.810%	$36.1347	$36.13	$36.15	$36.10
Purchase #2	$93.80	4.519%	$98.0388	$98.04	$98.05	$98.00
Purchase #3	$216.71	11.771%	$242.2189	$242.22	$242.20	$242.20
Purchase #4	$136.34	4.624%	$142.6444	$142.64	$142.65	$142.60
Purchase #5	$148.76	13.215%	$168.4186	$168.42	$168.40	$168.40
Purchase #6	$245.59	10.715%	$271.905	$271.91	$271.90	$271.90
Purchase #7	$39.98	5.257%	$42.0817	$42.08	$42.10	$42.10
7 purchase totals =	$912.93		$1,001.4421	$1,001.44	$1,001.45	$1,001.30