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	$180.72	12.663%	$203.6046	$203.60	$203.60	$203.60
Purchase #2	$217.52	3.140%	$224.3501	$224.35	$224.35	$224.40
Purchase #3	$179.41	5.327%	$188.9672	$188.97	$188.95	$189.00
Purchase #4	$65.76	10.812%	$72.87	$72.87	$72.85	$72.90
Purchase #5	$75.65	6.623%	$80.6603	$80.66	$80.65	$80.70
Purchase #6	$96.52	4.223%	$100.596	$100.60	$100.60	$100.60
Purchase #7	$172.31	9.123%	$188.0298	$188.03	$188.05	$188.00
7 purchase totals =	$987.89		$1,059.0780	$1,059.08	$1,059.05	$1,059.20