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	$187.42	11.519%	$209.0089	$209.01	$209.00	$209.00
Purchase #2	$37.61	4.744%	$39.3942	$39.39	$39.40	$39.40
Purchase #3	$196.93	4.546%	$205.8824	$205.88	$205.90	$205.90
Purchase #4	$188.92	11.473%	$210.5948	$210.59	$210.60	$210.60
Purchase #5	$184.73	12.210%	$207.2855	$207.29	$207.30	$207.30
Purchase #6	$126.46	13.736%	$143.8305	$143.83	$143.85	$143.80
Purchase #7	$96.63	9.225%	$105.5441	$105.54	$105.55	$105.50
7 purchase totals =	$1,018.70		$1,121.5404	$1,121.53	$1,121.60	$1,121.50