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	$38.52	6.623%	$41.0712	$41.07	$41.05	$41.10
Purchase #2	$152.55	4.846%	$159.9426	$159.94	$159.95	$159.90
Purchase #3	$96.95	7.512%	$104.2329	$104.23	$104.25	$104.20
Purchase #4	$171.74	7.454%	$184.5415	$184.54	$184.55	$184.50
Purchase #5	$151.60	12.808%	$171.0169	$171.02	$171.00	$171.00
Purchase #6	$168.69	8.130%	$182.4045	$182.40	$182.40	$182.40
Purchase #7	$236.57	12.586%	$266.3447	$266.34	$266.35	$266.30
7 purchase totals =	$1,016.62		$1,109.5543	$1,109.54	$1,109.55	$1,109.40