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	$92.60	10.661%	$102.4721	$102.47	$102.45	$102.50
Purchase #2	$39.83	6.700%	$42.4986	$42.50	$42.50	$42.50
Purchase #3	$245.84	4.373%	$256.5906	$256.59	$256.60	$256.60
Purchase #4	$185.65	6.111%	$196.9951	$197.00	$197.00	$197.00
Purchase #5	$108.88	3.168%	$112.3293	$112.33	$112.35	$112.30
Purchase #6	$221.94	7.449%	$238.4723	$238.47	$238.45	$238.50
Purchase #7	$27.50	6.546%	$29.3002	$29.30	$29.30	$29.30
7 purchase totals =	$922.24		$978.6582	$978.66	$978.65	$978.70