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	$35.85	9.475%	$39.2468	$39.25	$39.25	$39.20
Purchase #2	$174.89	3.316%	$180.6894	$180.69	$180.70	$180.70
Purchase #3	$150.88	3.596%	$156.3056	$156.31	$156.30	$156.30
Purchase #4	$233.60	9.544%	$255.8948	$255.89	$255.90	$255.90
Purchase #5	$201.49	6.634%	$214.8568	$214.86	$214.85	$214.90
Purchase #6	$149.37	7.580%	$160.6922	$160.69	$160.70	$160.70
Purchase #7	$147.49	7.597%	$158.6948	$158.69	$158.70	$158.70
7 purchase totals =	$1,093.57		$1,166.3804	$1,166.38	$1,166.40	$1,166.40