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	$181.44	8.200%	$196.3181	$196.32	$196.30	$196.30
Purchase #2	$137.92	6.368%	$146.7027	$146.70	$146.70	$146.70
Purchase #3	$21.28	13.224%	$24.0941	$24.09	$24.10	$24.10
Purchase #4	$219.96	13.683%	$250.0571	$250.06	$250.05	$250.10
Purchase #5	$235.75	12.368%	$264.9076	$264.91	$264.90	$264.90
Purchase #6	$143.62	10.338%	$158.4674	$158.47	$158.45	$158.50
Purchase #7	$168.35	4.253%	$175.5099	$175.51	$175.50	$175.50
7 purchase totals =	$1,108.32		$1,216.0569	$1,216.06	$1,216.00	$1,216.10