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	$214.39	6.420%	$228.1538	$228.15	$228.15	$228.20
Purchase #2	$101.43	7.709%	$109.2492	$109.25	$109.25	$109.20
Purchase #3	$104.93	8.414%	$113.7588	$113.76	$113.75	$113.80
Purchase #4	$13.41	12.818%	$15.1289	$15.13	$15.15	$15.10
Purchase #5	$238.77	7.527%	$256.7422	$256.74	$256.75	$256.70
Purchase #6	$218.99	10.666%	$242.3475	$242.35	$242.35	$242.30
Purchase #7	$86.72	10.761%	$96.0519	$96.05	$96.05	$96.10
7 purchase totals =	$978.64		$1,061.4323	$1,061.43	$1,061.45	$1,061.40