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	$172.26	11.801%	$192.5884	$192.59	$192.60	$192.60
Purchase #2	$108.93	3.400%	$112.6336	$112.63	$112.65	$112.60
Purchase #3	$82.95	3.251%	$85.6467	$85.65	$85.65	$85.60
Purchase #4	$96.46	9.116%	$105.2533	$105.25	$105.25	$105.30
Purchase #5	$76.34	12.460%	$85.852	$85.85	$85.85	$85.90
Purchase #6	$182.63	13.671%	$207.5973	$207.60	$207.60	$207.60
Purchase #7	$236.86	5.170%	$249.1057	$249.11	$249.10	$249.10
7 purchase totals =	$956.43		$1,038.6770	$1,038.68	$1,038.70	$1,038.70