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	$161.77	11.181%	$179.8575	$179.86	$179.85	$179.90
Purchase #2	$33.95	11.588%	$37.8841	$37.88	$37.90	$37.90
Purchase #3	$198.33	4.615%	$207.4829	$207.48	$207.50	$207.50
Purchase #4	$74.72	3.748%	$77.5205	$77.52	$77.50	$77.50
Purchase #5	$35.89	12.517%	$40.3824	$40.38	$40.40	$40.40
Purchase #6	$248.71	13.538%	$282.3804	$282.38	$282.40	$282.40
Purchase #7	$24.31	13.286%	$27.5398	$27.54	$27.55	$27.50
7 purchase totals =	$777.68		$853.0476	$853.04	$853.10	$853.10