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	$148.80	5.456%	$156.9185	$156.92	$156.90	$156.90
Purchase #2	$168.53	9.340%	$184.2707	$184.27	$184.25	$184.30
Purchase #3	$209.55	13.696%	$238.25	$238.25	$238.25	$238.30
Purchase #4	$228.38	4.349%	$238.3122	$238.31	$238.30	$238.30
Purchase #5	$132.27	4.151%	$137.7605	$137.76	$137.75	$137.80
Purchase #6	$171.36	7.745%	$184.6318	$184.63	$184.65	$184.60
Purchase #7	$18.76	11.110%	$20.8442	$20.84	$20.85	$20.80
7 purchase totals =	$1,077.65		$1,160.9879	$1,160.98	$1,160.95	$1,161.00