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	$55.96	11.771%	$62.5471	$62.55	$62.55	$62.50
Purchase #2	$206.26	7.193%	$221.0963	$221.10	$221.10	$221.10
Purchase #3	$81.85	9.829%	$89.895	$89.90	$89.90	$89.90
Purchase #4	$165.80	4.336%	$172.9891	$172.99	$173.00	$173.00
Purchase #5	$136.44	10.844%	$151.2356	$151.24	$151.25	$151.20
Purchase #6	$206.27	13.152%	$233.3986	$233.40	$233.40	$233.40
Purchase #7	$141.39	9.576%	$154.9295	$154.93	$154.95	$154.90
7 purchase totals =	$993.97		$1,086.0912	$1,086.11	$1,086.15	$1,086.00