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	$32.76	8.551%	$35.5613	$35.56	$35.55	$35.60
Purchase #2	$175.40	8.433%	$190.1915	$190.19	$190.20	$190.20
Purchase #3	$178.95	3.480%	$185.1775	$185.18	$185.20	$185.20
Purchase #4	$198.94	12.793%	$224.3904	$224.39	$224.40	$224.40
Purchase #5	$173.81	11.419%	$193.6574	$193.66	$193.65	$193.70
Purchase #6	$157.61	7.412%	$169.2921	$169.29	$169.30	$169.30
Purchase #7	$103.52	7.683%	$111.4734	$111.47	$111.45	$111.50
7 purchase totals =	$1,020.99		$1,109.7436	$1,109.74	$1,109.75	$1,109.90