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	$200.80	12.407%	$225.7133	$225.71	$225.70	$225.70
Purchase #2	$104.33	9.443%	$114.1819	$114.18	$114.20	$114.20
Purchase #3	$155.86	11.360%	$173.5657	$173.57	$173.55	$173.60
Purchase #4	$126.40	3.564%	$130.9049	$130.90	$130.90	$130.90
Purchase #5	$68.27	5.326%	$71.9061	$71.91	$71.90	$71.90
Purchase #6	$163.90	13.253%	$185.6217	$185.62	$185.60	$185.60
Purchase #7	$153.92	11.790%	$172.0672	$172.07	$172.05	$172.10
7 purchase totals =	$973.48		$1,073.9608	$1,073.96	$1,073.90	$1,074.00