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	$170.84	6.727%	$182.3324	$182.33	$182.35	$182.30
Purchase #2	$33.55	8.679%	$36.4618	$36.46	$36.45	$36.50
Purchase #3	$99.47	11.568%	$110.9767	$110.98	$111.00	$111.00
Purchase #4	$215.51	4.120%	$224.389	$224.39	$224.40	$224.40
Purchase #5	$114.32	11.396%	$127.3479	$127.35	$127.35	$127.30
Purchase #6	$102.32	3.325%	$105.7221	$105.72	$105.70	$105.70
Purchase #7	$38.70	4.239%	$40.3405	$40.34	$40.35	$40.30
7 purchase totals =	$774.71		$827.5704	$827.57	$827.60	$827.50