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	$64.61	13.410%	$73.2742	$73.27	$73.25	$73.30
Purchase #2	$87.44	9.354%	$95.6191	$95.62	$95.60	$95.60
Purchase #3	$169.65	9.413%	$185.6192	$185.62	$185.60	$185.60
Purchase #4	$239.27	13.364%	$271.246	$271.25	$271.25	$271.20
Purchase #5	$205.56	7.436%	$220.8454	$220.85	$220.85	$220.80
Purchase #6	$29.70	9.334%	$32.4722	$32.47	$32.45	$32.50
Purchase #7	$185.50	5.694%	$196.0624	$196.06	$196.05	$196.10
7 purchase totals =	$981.73		$1,075.1385	$1,075.14	$1,075.05	$1,075.10