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	$84.49	8.771%	$91.9006	$91.90	$91.90	$91.90
Purchase #2	$234.68	9.485%	$256.9394	$256.94	$256.95	$256.90
Purchase #3	$182.25	3.547%	$188.7144	$188.71	$188.70	$188.70
Purchase #4	$78.27	5.423%	$82.5146	$82.51	$82.50	$82.50
Purchase #5	$8.75	11.611%	$9.766	$9.77	$9.75	$9.80
Purchase #6	$245.89	5.598%	$259.6549	$259.65	$259.65	$259.70
Purchase #7	$184.55	6.355%	$196.2782	$196.28	$196.30	$196.30
7 purchase totals =	$1,018.88		$1,085.7681	$1,085.76	$1,085.75	$1,085.80