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	$177.86	12.462%	$200.0249	$200.02	$200.00	$200.00
Purchase #2	$52.43	11.661%	$58.5439	$58.54	$58.55	$58.50
Purchase #3	$33.54	11.180%	$37.2898	$37.29	$37.30	$37.30
Purchase #4	$96.82	8.428%	$104.98	$104.98	$105.00	$105.00
Purchase #5	$177.27	7.638%	$190.8099	$190.81	$190.80	$190.80
Purchase #6	$181.84	4.583%	$190.1737	$190.17	$190.15	$190.20
Purchase #7	$160.58	3.602%	$166.3641	$166.36	$166.35	$166.40
7 purchase totals =	$880.34		$948.1863	$948.17	$948.15	$948.20