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	$203.67	3.311%	$210.4135	$210.41	$210.40	$210.40
Purchase #2	$6.73	8.565%	$7.3064	$7.31	$7.30	$7.30
Purchase #3	$118.65	7.837%	$127.9486	$127.95	$127.95	$127.90
Purchase #4	$166.54	6.665%	$177.6399	$177.64	$177.65	$177.60
Purchase #5	$179.45	7.721%	$193.3053	$193.31	$193.30	$193.30
Purchase #6	$168.85	13.195%	$191.1298	$191.13	$191.15	$191.10
Purchase #7	$112.52	9.582%	$123.3017	$123.30	$123.30	$123.30
7 purchase totals =	$956.41		$1,031.0452	$1,031.05	$1,031.05	$1,030.90