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	$163.66	4.699%	$171.3504	$171.35	$171.35	$171.40
Purchase #2	$54.71	11.336%	$60.9119	$60.91	$60.90	$60.90
Purchase #3	$118.92	3.864%	$123.5151	$123.52	$123.50	$123.50
Purchase #4	$94.52	3.253%	$97.5947	$97.59	$97.60	$97.60
Purchase #5	$191.40	9.332%	$209.2614	$209.26	$209.25	$209.30
Purchase #6	$115.71	6.759%	$123.5308	$123.53	$123.55	$123.50
Purchase #7	$241.28	3.329%	$249.3122	$249.31	$249.30	$249.30
7 purchase totals =	$980.20		$1,035.4765	$1,035.47	$1,035.45	$1,035.50