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	$185.53	12.652%	$209.0033	$209.00	$209.00	$209.00
Purchase #2	$172.60	7.671%	$185.8401	$185.84	$185.85	$185.80
Purchase #3	$49.59	3.278%	$51.2156	$51.22	$51.20	$51.20
Purchase #4	$86.84	3.735%	$90.0835	$90.08	$90.10	$90.10
Purchase #5	$143.90	5.470%	$151.7713	$151.77	$151.75	$151.80
Purchase #6	$146.88	13.861%	$167.239	$167.24	$167.25	$167.20
Purchase #7	$215.25	10.226%	$237.2615	$237.26	$237.25	$237.30
7 purchase totals =	$1,000.59		$1,092.4143	$1,092.41	$1,092.40	$1,092.40