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	$61.52	4.391%	$64.2213	$64.22	$64.20	$64.20
Purchase #2	$161.63	9.715%	$177.3324	$177.33	$177.35	$177.30
Purchase #3	$168.42	13.759%	$191.5929	$191.59	$191.60	$191.60
Purchase #4	$106.53	6.417%	$113.366	$113.37	$113.35	$113.40
Purchase #5	$188.87	4.284%	$196.9612	$196.96	$196.95	$197.00
Purchase #6	$103.25	6.638%	$110.1037	$110.10	$110.10	$110.10
Purchase #7	$233.79	10.308%	$257.8891	$257.89	$257.90	$257.90
7 purchase totals =	$1,024.01		$1,111.4666	$1,111.46	$1,111.45	$1,111.50