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	$161.49	6.457%	$171.9174	$171.92	$171.90	$171.90
Purchase #2	$55.80	9.551%	$61.1295	$61.13	$61.15	$61.10
Purchase #3	$104.41	5.359%	$110.0053	$110.01	$110.00	$110.00
Purchase #4	$59.76	13.603%	$67.8892	$67.89	$67.90	$67.90
Purchase #5	$63.43	4.188%	$66.0864	$66.09	$66.10	$66.10
Purchase #6	$172.76	5.813%	$182.8025	$182.80	$182.80	$182.80
Purchase #7	$20.81	4.314%	$21.7077	$21.71	$21.70	$21.70
7 purchase totals =	$638.46		$681.5380	$681.55	$681.55	$681.50