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	$138.94	8.554%	$150.8249	$150.82	$150.80	$150.80
Purchase #2	$148.38	13.377%	$168.2288	$168.23	$168.25	$168.20
Purchase #3	$62.48	4.874%	$65.5253	$65.53	$65.55	$65.50
Purchase #4	$169.97	10.670%	$188.1058	$188.11	$188.10	$188.10
Purchase #5	$194.65	10.761%	$215.5963	$215.60	$215.60	$215.60
Purchase #6	$17.76	3.173%	$18.3235	$18.32	$18.30	$18.30
Purchase #7	$225.59	10.529%	$249.3424	$249.34	$249.35	$249.30
7 purchase totals =	$957.77		$1,055.9470	$1,055.95	$1,055.95	$1,055.80