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	$214.59	3.541%	$222.1886	$222.19	$222.20	$222.20
Purchase #2	$218.56	13.819%	$248.7628	$248.76	$248.75	$248.80
Purchase #3	$193.27	9.858%	$212.3226	$212.32	$212.30	$212.30
Purchase #4	$133.69	12.697%	$150.6646	$150.66	$150.65	$150.70
Purchase #5	$69.90	12.692%	$78.7717	$78.77	$78.75	$78.80
Purchase #6	$105.54	11.798%	$117.9916	$117.99	$118.00	$118.00
Purchase #7	$233.48	9.466%	$255.5812	$255.58	$255.60	$255.60
7 purchase totals =	$1,169.03		$1,286.2831	$1,286.27	$1,286.25	$1,286.40