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	$173.75	7.803%	$187.3077	$187.31	$187.30	$187.30
Purchase #2	$23.34	4.288%	$24.3408	$24.34	$24.35	$24.30
Purchase #3	$127.39	5.401%	$134.2703	$134.27	$134.25	$134.30
Purchase #4	$27.79	12.569%	$31.2829	$31.28	$31.30	$31.30
Purchase #5	$55.66	6.464%	$59.2579	$59.26	$59.25	$59.30
Purchase #6	$27.50	7.149%	$29.466	$29.47	$29.45	$29.50
Purchase #7	$196.75	11.649%	$219.6694	$219.67	$219.65	$219.70
7 purchase totals =	$632.18		$685.5950	$685.60	$685.55	$685.70