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	$202.48	6.442%	$215.5238	$215.52	$215.50	$215.50
Purchase #2	$194.36	10.683%	$215.1235	$215.12	$215.10	$215.10
Purchase #3	$34.59	7.675%	$37.2448	$37.24	$37.25	$37.20
Purchase #4	$171.39	9.537%	$187.7355	$187.74	$187.75	$187.70
Purchase #5	$207.59	10.162%	$228.6853	$228.69	$228.70	$228.70
Purchase #6	$16.59	10.572%	$18.3439	$18.34	$18.35	$18.30
Purchase #7	$177.88	6.209%	$188.9246	$188.92	$188.90	$188.90
7 purchase totals =	$1,004.88		$1,091.5814	$1,091.57	$1,091.55	$1,091.40