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	$119.57	3.427%	$123.6677	$123.67	$123.65	$123.70
Purchase #2	$208.88	9.361%	$228.4333	$228.43	$228.45	$228.40
Purchase #3	$76.84	8.811%	$83.6104	$83.61	$83.60	$83.60
Purchase #4	$27.27	7.823%	$29.4033	$29.40	$29.40	$29.40
Purchase #5	$168.96	12.211%	$189.5917	$189.59	$189.60	$189.60
Purchase #6	$240.83	11.789%	$269.2214	$269.22	$269.20	$269.20
Purchase #7	$78.60	4.726%	$82.3146	$82.31	$82.30	$82.30
7 purchase totals =	$920.95		$1,006.2424	$1,006.23	$1,006.20	$1,006.20