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	$171.50	10.420%	$189.3703	$189.37	$189.35	$189.40
Purchase #2	$150.29	11.514%	$167.5944	$167.59	$167.60	$167.60
Purchase #3	$239.83	10.453%	$264.8994	$264.90	$264.90	$264.90
Purchase #4	$59.27	4.671%	$62.0385	$62.04	$62.05	$62.00
Purchase #5	$117.88	10.256%	$129.9698	$129.97	$129.95	$130.00
Purchase #6	$246.30	3.782%	$255.6151	$255.62	$255.60	$255.60
Purchase #7	$109.86	12.375%	$123.4552	$123.46	$123.45	$123.50
7 purchase totals =	$1,094.93		$1,192.9427	$1,192.95	$1,192.90	$1,193.00