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	$169.64	6.593%	$180.8244	$180.82	$180.80	$180.80
Purchase #2	$222.68	6.381%	$236.8892	$236.89	$236.90	$236.90
Purchase #3	$96.53	4.508%	$100.8816	$100.88	$100.90	$100.90
Purchase #4	$92.33	7.764%	$99.4985	$99.50	$99.50	$99.50
Purchase #5	$231.34	3.727%	$239.962	$239.96	$239.95	$240.00
Purchase #6	$212.44	13.832%	$241.8247	$241.82	$241.80	$241.80
Purchase #7	$46.34	10.647%	$51.2738	$51.27	$51.25	$51.30
7 purchase totals =	$1,071.30		$1,151.1542	$1,151.14	$1,151.10	$1,151.20