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	$112.66	9.227%	$123.0551	$123.06	$123.05	$123.10
Purchase #2	$110.80	9.786%	$121.6429	$121.64	$121.65	$121.60
Purchase #3	$144.44	6.139%	$153.3072	$153.31	$153.30	$153.30
Purchase #4	$218.77	11.349%	$243.5982	$243.60	$243.60	$243.60
Purchase #5	$99.43	5.357%	$104.7565	$104.76	$104.75	$104.80
Purchase #6	$128.80	3.693%	$133.5566	$133.56	$133.55	$133.60
Purchase #7	$221.61	4.556%	$231.7066	$231.71	$231.70	$231.70
7 purchase totals =	$1,036.51		$1,111.6231	$1,111.64	$1,111.60	$1,111.70