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	$219.33	10.746%	$242.8992	$242.90	$242.90	$242.90
Purchase #2	$101.59	10.112%	$111.8628	$111.86	$111.85	$111.90
Purchase #3	$118.93	5.598%	$125.5877	$125.59	$125.60	$125.60
Purchase #4	$165.55	10.133%	$182.3252	$182.33	$182.35	$182.30
Purchase #5	$97.56	7.122%	$104.5082	$104.51	$104.50	$104.50
Purchase #6	$237.61	13.638%	$270.0153	$270.02	$270.00	$270.00
Purchase #7	$182.42	4.664%	$190.9281	$190.93	$190.95	$190.90
7 purchase totals =	$1,122.99		$1,228.1265	$1,228.14	$1,228.15	$1,228.10