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	$63.84	6.576%	$68.0381	$68.04	$68.05	$68.00
Purchase #2	$185.31	7.594%	$199.3824	$199.38	$199.40	$199.40
Purchase #3	$106.79	9.546%	$116.9842	$116.98	$117.00	$117.00
Purchase #4	$207.64	7.168%	$222.5236	$222.52	$222.50	$222.50
Purchase #5	$72.76	12.860%	$82.1169	$82.12	$82.10	$82.10
Purchase #6	$187.44	12.772%	$211.3798	$211.38	$211.40	$211.40
Purchase #7	$207.83	9.386%	$227.3369	$227.34	$227.35	$227.30
7 purchase totals =	$1,031.61		$1,127.7619	$1,127.76	$1,127.80	$1,127.70