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	$123.55	11.111%	$137.2776	$137.28	$137.30	$137.30
Purchase #2	$100.39	13.104%	$113.5451	$113.55	$113.55	$113.50
Purchase #3	$153.84	11.374%	$171.3378	$171.34	$171.35	$171.30
Purchase #4	$191.72	5.281%	$201.8447	$201.84	$201.85	$201.80
Purchase #5	$151.40	13.839%	$172.3522	$172.35	$172.35	$172.40
Purchase #6	$26.60	3.159%	$27.4403	$27.44	$27.45	$27.40
Purchase #7	$240.77	5.437%	$253.8607	$253.86	$253.85	$253.90
7 purchase totals =	$988.27		$1,077.6584	$1,077.66	$1,077.70	$1,077.60