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	$32.27	11.417%	$35.9543	$35.95	$35.95	$36.00
Purchase #2	$167.98	12.158%	$188.403	$188.40	$188.40	$188.40
Purchase #3	$139.68	9.707%	$153.2387	$153.24	$153.25	$153.20
Purchase #4	$250.90	13.381%	$284.4729	$284.47	$284.45	$284.50
Purchase #5	$80.47	11.791%	$89.9582	$89.96	$89.95	$90.00
Purchase #6	$77.97	7.346%	$83.6977	$83.70	$83.70	$83.70
Purchase #7	$208.51	5.473%	$219.9218	$219.92	$219.90	$219.90
7 purchase totals =	$957.78		$1,055.6466	$1,055.64	$1,055.60	$1,055.70