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	$95.65	10.343%	$105.5431	$105.54	$105.55	$105.50
Purchase #2	$101.88	4.855%	$106.8263	$106.83	$106.85	$106.80
Purchase #3	$196.90	4.585%	$205.9279	$205.93	$205.95	$205.90
Purchase #4	$198.38	3.692%	$205.7042	$205.70	$205.70	$205.70
Purchase #5	$84.35	11.280%	$93.8647	$93.86	$93.85	$93.90
Purchase #6	$109.92	5.818%	$116.3151	$116.32	$116.30	$116.30
Purchase #7	$42.38	10.467%	$46.8159	$46.82	$46.80	$46.80
7 purchase totals =	$829.46		$880.9972	$881.00	$881.00	$880.90