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	$190.69	8.512%	$206.9215	$206.92	$206.90	$206.90
Purchase #2	$123.60	6.548%	$131.6933	$131.69	$131.70	$131.70
Purchase #3	$94.87	4.473%	$99.1135	$99.11	$99.10	$99.10
Purchase #4	$142.73	13.424%	$161.8901	$161.89	$161.90	$161.90
Purchase #5	$31.73	9.431%	$34.7225	$34.72	$34.70	$34.70
Purchase #6	$13.63	5.788%	$14.4189	$14.42	$14.40	$14.40
Purchase #7	$158.57	9.609%	$173.807	$173.81	$173.80	$173.80
7 purchase totals =	$755.82		$822.5668	$822.56	$822.50	$822.50