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	$194.65	7.702%	$209.6419	$209.64	$209.65	$209.60
Purchase #2	$81.80	5.704%	$86.4659	$86.47	$86.45	$86.50
Purchase #3	$176.59	6.126%	$187.4079	$187.41	$187.40	$187.40
Purchase #4	$238.76	7.307%	$256.2062	$256.21	$256.20	$256.20
Purchase #5	$71.73	9.179%	$78.3141	$78.31	$78.30	$78.30
Purchase #6	$161.98	11.358%	$180.3777	$180.38	$180.40	$180.40
Purchase #7	$44.26	12.564%	$49.8208	$49.82	$49.80	$49.80
7 purchase totals =	$969.77		$1,048.2345	$1,048.24	$1,048.20	$1,048.20